The advantage of being affiliated is that you have the insurance cover for your club and good support from B.C.
The first year is the most expensive, after that there are reductions in the affiliation fee for every member you have of B.C.
I also think that B.C. give you some free bronze memberships to distribute to your volunteers. Every region has a B.C. manager, if you get in touch with B.C. they will tell you who your regional manager is and they would help you set up an official club. Good luck whatever you decide to do.
