Most of the BCF members are US based.
I estimate there between 300 and 400 members in the UK.
Some time back I was curious and used the member profile search facility to see who was located in Scotland, and found around 20 members.
Plugging in "UK" for the location turned up another 220; "England" another 80 and even "London" pulled up 25 or so. And 10 were in "Wales". Only a couple said they were from "Britain"....
But some of this was double counting "London, England, UK" would show up on all three, and some weren't right at all- one or two of the "Wales" responses were for New South "Wales"....
Some time when I'm really bored I might try it for France, and Germany, or ...