You can join the IBC if your in the UK. It is the International Betta Club
There is also a European Club called the European Halfmoon Betta Breeders Club (EHBBC
). I do believe that breeders of other tail types can also join.
Joep who is the author of the Bettaterritory site is a member of the EHBBC, I believe. He is located in the Netherlands. You might try contacting him for more information about the European clubs/groups.