Try this site
http://www.killi.co.uk/
Its an awesome site thats based in the UK. He has a for sale section for UK and a fish & egg listing. If you don't see what you are looking for, you could always email him. With his site being so incredibly comprehensive, I am quite sure he has lots of killie contacts.
Oh and here is the
http://www.bka.org.uk/ (British Killifish Association)