I have been looking around on the web and am on the point of ordering some Bilt Hamber Auto-clay. Two 200g packs, one regular, one soft, for £20.90 and it is very well reviewed. I am new to claying and want something that is not likely to damage my paintwork but that will bring it up looking clean and smooth.
I am tempted by their Auto-balm wax too...
I use BH products in my classic car restorations and they are really good and come highly recommended.