My wife was looking for some squash seeds earlier this year and found the
variety she wanted was only available from the USA/Oregon . They took quite
a long time to deliver (4-8 weeks) but she says they were quite cheap
compared to UK prices. She thought others might be interested..

http://www.seedfest.co.uk/

I'm not connected with this company - I'm not even a paricularly keen
gardener!