Check out the SBS Reserve Website - its got the answers to most of your questions and they are mega approachable so you can even give them a call. The phone number is on the Website: www.army.mod.uk/uksf then click on Special Forces Soldier (Reserve) and SBS(R). They like to recruit from the RMR. But will accept any Reserve/TA with the right fitness. Training is the same as the Regulars but modular. You must hit 4KPH on Phase 1; the Trees phase is required for Phase 2. Military experience is prefered but not essential. They do not take direct civilian entry - so you must belong to a Reserve/TA Unit to start training.