Far as I can tell they seem to be one of the cheapest and never had any trouble with resin or silicone bought from them. Last batch of general purpose casting resin I got a couple weeks back came to about £55 shipped for 10kg
You know what having looked through the other websites I'd give Tomps a go, great prices and decent looking stuff. Wish I'd seen their fast cast resin before I stocked up on regular stuff from MB. meh