Have you got a copy of the NFRS breeders list? If not, you can e-mail [email protected] and it'll ping you a copy back automatically.
My copy is probably very outdated so I don't know how many of these people are still breeding pearls but it lists:
Asbru Stud in Lincolnshire (cinnamon pearl only - not sure if they're related?)
Darkstar Stud in Suffolk
Holywood Stud in Wilts
Amicus Rattery in Devon
Aphrodite Stud in Glasgow
Kropotkin Stud in London