My West of England geese came from breeders on the Hampshire/Wiltshire border. They're not huge though and I would guess they have already sorted their set up for this year (I.e. unlikely to have a spare female hanging around - especially if you're not going to breeding from her) but I can send you the details if you want. More usefully, they're heavily involved in the British Waterfowl Association (he's the current president) so they might know other sources of geese nearby.
What breed are you wanting?