I would like to learn more about ammunition technicians and there roles and what's involved in there training

I'm no expert so I asked one for you and he replied as follows:

In short, an ammunition technician (AT) is the British Army’s Subject Matter Expert on all things explosive. From storing safely; through life surveillance; and end of life disposal. Ammunition technicians inspect units storage and issue licences to store and move ammunition and explosive natures. Due to their in depth working knowledge of ammunition and explosive natures they also investigate failures or incidents involving munitions.

AT Senior Non-Commissioned Officers and Ammunition Technician Officers are eligible to conduct Explosive Ordnance Device (EOD) duties, assisting the police with explosive incidents in the UK involving conventional munitions and improvised explosive devices.

An ATs training stats with the Class two course. Learning about basic chemistry and physics, moving onto all the natures currently in service in the British forces. Further on, the Class one course teaches them about storage, guided munitions and conventional munition disposal. Seniors are then eligible for the Defence EOD Operators course in order to conduct EOD duties in support of the police.

For more information on ATs and Royal Engineer bomb disposal have a look at 11EOD&S on Instagram, the Felix fund charity, and an upcoming “inside the bomb squad” tv documentary.

Once you have completed your training is it then possible to join 23 parachute engineer regiment? And if so what is there role in that regiment

At what rank are you eligible for defense EOD Operators course

Some more information from an expert: Here is my summary of the AT trade.

The Role of the Ammunition Technicians within the British army is to be subject matter experts on ammunition and explosives. We have lots of different job roles on offer and our day to day work and vary depending on where you are.
Some of the things an AT can do within their career.
Being the British Army’s explosives experts we can apply our knowledge of how explosives devices work to dispose of threats posed by IED’s. In the UK we have teams based all around the country ready to assist local authorities of any potential threats. You will at first learn to drive the blue light emergency response vehicles as well as the Remote Controlled Vehicles that are used to carry out taskings and further up in ranks can wear the bomb suit and be in charge of the taskings where you will also get extra pay. You could potentially be called out to everything suspect packages, pipe bombs, old buried munitions or car bombs.
We also have teams available to provide the same capability oversees. These teams train to work in the field with the Army’s quick reaction force and will work out of armoured vehicles and have a more military focus. People here tend to try to go for the all arms commando course or the P Company course. We also have people who work closely with special forces to provide an Improvised explosive device capability for them.
It is also our role to carry out large scale demolitions of ammunition that is no longer required or past it’s safe use dates. These demolitions can take several people days to set up depending on the number of items that are required.
Ammunition Technicians can work in Military intelligence and help carry out forensic analysis on various attacks. Ammunition Technicians can carry out investigations into any incidents involving ammunition if the ammunition fails to function as intended or units using the ammunition report incidents. Later on in they can assist on development and procurement of new types of ammunition for the Army.
Wherever guided missiles are test fired be it in the UK or overseas and Ammunition Technician must be present to report on any faults or assist in the disposal of any missiles that fail to function. We can also support the Army’s large scale exercises processing ammunition for them to ensure it is safe to be used. This gives good opportunities to travel and will usually involve staying in hotels around the world.
We have specialists in Chemical Warfare who helped assist with the clean up and investigation after the poisoning in Salisbury.
Our trade have plenty of opportunities to travel and can be posted to several different places to have a varied career, we never have to just keep doing the one same thing over and over.

The course it’s self is about 29 weeks long and is taught at MOD Kineton and is split up into the following:

Shrivenham – 7 Weeks
Authorised Representative – 2 Weeks
Land Service Ammunition – 7 Weeks (4 Modules)
Storage – 2 Week
Surveillance – 6 Weeks (3 weeks in labs)
Disposals – 3 Weeks
HAZMAT – 1 Week
Graduation – 1 Week

Shrivenham - At The Defence Academy of the UK Shirvenham you be taught basic principles of ammunition design as well as various subjects to give you a base level of knowledge of knowledge to help understand how ammunition works. These subjects include: Maths, Chemistry, Explosives Chemistry, Metallurgy, Electronics and Ballistics. This is all taught by professors from Cranfield university who are all leaders in their fields. Whilst at Shrivenham you will get to create nitrocellulose a single based propellent explosive. You will also have access to the Ammunition, Artillery and tank museums there. Also the accommodation is very good and the bar is cheap.
Authorised Representative – During this phase you will be taught the rules and regulations for the movement of Class 1 dangerous goods on roads and rail within the UK. You’ll be taught how to carry out the proper inspections and how to fill out the paperwork required for before and after journeys.
Land Service Ammunition - You will be taught every piece of ammunition in current service in the British Army. You will be taught everything from small arms ammunition, grenades, flares, mortars, fuses, guided missiles, tank rounds and demolition equipment. You will be taught everything from what the explosives inside the ammunition are, how they initiate, as well as safety feature. You’ll be assed on your knowledge of the ammo, your ability to look up information on it as well as being able to recognise different items from pictures.
Storage – You will be taught the regulations for the storage of ammunition and will have a practical assessment on inspecting an explosive storehouse.
Surveillance – Here you will have to show you can apply your knowledge of ammunition and how to safely handle and inspect ammunition. You will be assessed on your ability to carry out safety inspections on various items. You will also be shown how to work in an ammunition processing building. You will have to plan out how you would run a lab for an item and then everyone will take turns in charge running the lab whilst handling live ammunition.
Disposals – First you will run through some of the safety elements required for demolitions and then practice drills for safely prepping explosive charges. Once you have shown you can safely set up a demolition pit you will then get to work disposing of live ammunition by blowing it up.
HAZMAT – Similar to AR you will be taught the rules and regulations for all classes of dangerous goods for driving on public roads.
Graduation – You will practice running through the graduation day where families can come down and you can taught them through what you have learned and then show them a live explosives demolition before having a meal together.

Kineton contains the largest ammunition storage facility in western Europe. The camp its self is about a 20 minute drive from the nearest town so if you can drive that helps but if not the army will teach you to get Cat B, C and C+E Licences.
On completion of the class 2 course you will be promoted to LCpl and get to choose where you would like to be posted to. Promotion within the trade is relatively quick however should not be considered guaranteed.

Another AT expert wrote this: As an Ammunition Technician you will be the subject matter expert SME, when it comes to all ammunition with in the British Army. This includes, understanding how to correctly store, transport and handle ammunitions and explosive substances, as well as safely running demolitions. Where ever there’s a large amount of ammunition there will be an ammunitions technician making sure everything is safe and being carried out correctly.

To become an Ammunition Technician or Ammo Tech as they are known in the army. You will need to already have five GCSE’s grade C or level 4 and above including Math, English and Science. Then you will need to pass a Technical Selection Test (TST) which can be taken at the any Army Assessment Centre. If you are successful in this test you will then be booked in to attend the Ammo Tech selection board. This board is set over a three day period in Kineton. Here you will sit a Mechanical reasoning test, a referencing test, a mathematics test (no harder than GCSE level). Conduct a planning Exercise as well as a presentation on a subject of your choice. Finally you will sit down for an interview with three military assessors. At the end of the final day you find out if you have been successful in all areas and can go on to begin training as an ammunition technician.

Phase 2 DST Leconsfied where you will complete the combat logistitian course, getting your driving licenses, from CAT B to CAT C+E. you will now begin your phase2 trade training which will start with 2 months in the defence university Shrivenham, here you will hone in on your maths, physics, chemistry, mechanical and other skills and begin to understand how ammunition works.
Once you have complete your first 8 weeks of training to Shrivenham you will move to DEMS Kineton to complete the final phase of your trade training, here you will learn about all ammunition in the British Army, how to correctly Store it, oversee missile firings, maintain it, Move it by road and Rail and how you use Demolitions. You will constantly be tested throughout each phase with theory exams, referencing exams and practical exams.

After these 8 months of training and hard work you will leave training as a LCpl not a Pte. The level of pay you will be on, is higher than most other trades not only in the RLC but within the British Army, you can also go on to gain qualifications in explosive ordinance engineering up to a master degree level.