You could also contact Simon Unwin at firstname.lastname@example.org They have a large database (I think viewable on their website) I have had two or three really excellent sails from them at very reasonable prices and given that they are sailmakers they seem to know what they are talking about.
Look at the sailmakers. We bought a very new No 2 from Banks that I would guess was either not right for a racer or wasn't collected or something. Cost £200. Less than half price for a crackly new sail. You of course have to be lucky that they have the right size. Banks list theirs on their website.
http://www.secondhand-sails.co.uk/, seems to have a good range, although you'd probably have to travel to see them. Like mentioned above, your local sailmakers may have second hand sails even if not advertised.
http://www.seateach.com/ - large stock of very reasonably priced second hand and new sails. Website list is sometimes a bit out of date, but you just enter the size (luff and foot) you are looking for.