Can you do multiple specialties like diving, commandos and if so how would that work with say air assault, commandos.

Hi there,
From a Royal Engineers perspective, yes you can certainly do multiple specialities. I have friends who have completed the Commando Course, P Company and the Dive Course. They can then be posted to 23 Parachute Engineer Regiment or 24 Commando Engineer Regiment. Having done the Dive Course, you are then a specialist diver within any RE Regiment. There are other specialities too - becoming a professionally qualified engineer, a geo specialist, EOD (Explosive Ordnance Disposal) and Search.
How it tends to work is that you express interest and get recommended for certain courses in your annual report. After basic training, if put down as your preference to go to a more specialist unit then you would do the course after you finish you Corps or Regimental specific training (aka "Phase 2").
Hope that helps. The Army website should be able to give some more information as well.

Peter,

Throughout your career you will do various Adventurous training including courses and diving is a popular option for military personnel. With regards to commandos, yes the commando course is open for a lot of the army to jump on!

The only restriction will be your units forecast of events and where they are due to go etc. Operations will take priority as you can imagine

Regards