They have a lot of cheap frames at this site in the £4.95 price range, but I found this pair of TITANIUM frames on almost the last page. Add £1 for single vision lenses and £3.95 for shipping and you have natty space age specs for under a tenner. Or you can pay more for coated lenses (£2) or fancy lightweight high-index material ones (up to £28) to make full use of the light weight aspect of the frames.
I bought some with the clunky lenses but coated for £10.90 all in. They are posted from Pakistan, so it does take awhile.