http://thistlecavies.tripod.com/index.html that's a link to a guinea pig rescue if that's any help
It might be worth phoning up your local SSPCA and see what they have as I'm not sure the website is updated regularly. Keep an eye out for ads on gumtree as well, I've seen quite a few pop up in the past, poor wee things.
Guinea pigs make fantastic pets - I really miss my boys