How long would it be if later down the line you wanted to commission having previously served in the infantry?

Hi, it depends. There are 2 routes: Direct Entry (ie Under 28yrs old) -as a serving soldier, you'd need the recommendations and support from your chain of command. You'd then go through the same pipeline as a civilian (the Army Officer Selection Board (AOSB) process). You might be awarded a Potential Officer Development (PODC) pass on AOSB Briefing which is an awesome course held at Worthy Down prior to attending the Main Board. You'd attend the 44 wk Commissioning course at Sandhurst (RMAS) and commission as a 2Lt. If you have reached Cpl your pay would probably be more than most Officer Cadets (OCdts) at Sandhurst!! Or you wait until you reach the rank of Sgt and then you could look at going the Late Entry Officer route - when you would commission as a Capt and only spend a few wks at RMAS. There is no guarantee for either route and it depends on you as a person, how much you want it and how much you put into getting it (research, time,effort etc). I hope this at least gives you an idea though.