In reply to mcflute:
15,30and 45 degree symmetric system board with a variety of wooden holds plus two sizes of foot holds. Hold would be the principle cost. Campus board, a few finger boards and some scaffolding for pull ups rings, trx. Set of second hand weight lifting sets and a set of used kettle bells. Crash matting at about 100 quid per sq meter.
Insurance -get quotes. Public liability, professional indemnity, and the other one commonly insure up to 5 million per event but how much it costs depends on the proposal
Don't forget rates on top of rent, though a charity might find a way out of that?
And how are you going to control entry with mis-users key code sharing online or key fob sharing? Or tailgating. Web cams? Get in touch if you want to use biometrics. I can help there. A robust system will keep insurance costs down.
Hope it works out for you.