I've had a few sales through facebook - both from my facebook store (using payvment, like the last poster said) and a few general enquiries leading to commisions. I thinks it's one of the best pieces of promo I have right now, the return I get from the time spent is much better for me than things like twitter
You can buy resin in the UK from loads of places including fred aldous and silver clay.co.uk. You'll also prob find it in craft store and sometimes hardware stores. If you're buying a lot it's worth looking up some non-craft suppliers, for example some boat repair/building websites so bulk resin a lot cheaper than the craft stores. Good luck - I work with resin too and I'm based up in scotland, haven't found any problems geting supplies yet!