Just a quick entry this morning, but I thought it would be worth mentioning Rainbow Silks, not least because I have just spend some money with them.
Based in Great Missenden (a great place to visit because the Roald Dahl museum has a great tea shop and Rainbow Silks has a shop there - as well as an on line shop) they have a fabulous range of all things arty. Great products that can be difficult to source elsewhere. I have ordered a new line in marbling paints (to try out at a workshop I am running in a couple of weeks) - they work on fabric but are not washable. Probably best for papers and sketch booking. But worth a look.
So, I have put the link up on the links section on the right hand side in case anyone wants to have a look..