I think you need a manager/trainer who is licenced, and then you can apply for one through BBBofC....but im not sure, there are more qualified people on here who can probably give you a better answer. i think amatuer experience helps, but is not a definite criteria
the license costs £95 pounds mate and the medical you need to go through is in the £750 range, ive just went through it all recently to get my license, then you need to go to a meeting infront of the BBB of C and they will question you and decide whether or not to give you a license. If you have amatuer experience you should get one no problem
do the bbbc come and inspect the gym like the aba? If so what are the basic requirements for the gym. for example, will the bbbc want the gym to have showers? etc.