I feel really bad that I've put ppl off working with silk by moaning so much! The problem was that I didn't do as Dama suggests and put the interfacing on before cutting, I'm sure if I'd done that it would have been a lot less trouble! Or if I'd used the Fray Check product that was also recommended.
Just to clarify as well, the jewel toned silks are shot silk, I think that's the word for it, it's not the fine, slippery stuff, it's thick and the weave is really obvious. The fibres are really thick, like 1/16" and that's why the fraying was such a problem.