Are you near a branch of JL? If so, their assistants in the furnishing fabric dept are really helpful, especially if you go when it's not busy - Sunday morning maybe.
Just take in a pillow case and ask for suggestions of styles that would co-ordinate. They'll find sample books you wouldn't have by yourself, and you can order samples to be posted to you. It's then up to you if you decide to have curtains made there or just buy the fabric and have them made elsewhere.
Great, going to London tomorrow so am sure I can find a JL to go into and ask. There's not one where I live but if I don't find one in London then I can make a day's shopping trip elsewhere and get to one.
Lillyloo - think you're right about the curtains needing to be plain. Thanks.