It seems unlikely to find enough J/30s there to race one-design.
Earlier this year, I corresponded with Ron & Penny Hunt of Barbados, who own a 1979 J/30 built by Westerly in England (hull number WM15379). Alan Johnstone confirmed only that Bob Johnstone recalled 20 to 30 J/30s were built by Westerly in the early days, but had no other information in the archives.
An early J/30 Journal by
J/Boats reported that hull #10 was shipped Westerly Marine to serve as a model as they began production in the UK. She was named Juggernaut and entered the Fastnet Race skippered by Andy Cassel and crewed by Tim Levett, a project manager from Westerly. It was later renamed Judicious and registered to Capt. Jock Smith of Dublin, Ireland circa 1993 (Capt. Smith was reported deceased in 1996). The only current information I have on any J/30 owners is hull #251 (TPI/WM?) Katla, owned by Martin and Ian Pavey and located in Ipswich, northeast of London.
Where are you? Do you know of any others?