Hey Danny.
I was at Riders in Brislington, Bristol on Saturday.
They had a big sign over the door with "south west chapter"
A bit later bikers turned up with the same written on their waistcoats so I guess it's some kind of club.
By the looks of it the only prerequisite is you must own a Harley, have a beard, weigh at least 18 stone and be over 50.
Hope this helps.