Around the Helston, falmouth, Truro area.
Not pets at home!!
You can get a list of NFRS registered ratterys by emailing breeders@nfrs.org that may help. You may also try asking on the fancy rats forums, if you haven't already:
http://www.fancy-rats.co.uk/community/ as even if the breeders are not based near you, they do a lot of travelling to various rat shows and to swop rats to prevent inbreeding so it maybe that you could get help with transport.
There is
http://www.dumbotasticrats.com/ near plymouth if you don't mind travelling to there.
There is also a rescue in cornwall -
http://www.freewebs.com/rattyrescue/ if you would like to give them a go. Rescues often have unwanted litters as well, if you were wanting them as babies and will be handled and friendly like those from a breeder.
pets question and answers,www.5d2d.com There is also
http://www.rspcacornwall.org.uk/ that may be worth a ring.
Good luck in your rat search!
Search it up on Google