I'd like to mention Allparts too, I get pretty much equal amounts of stuff from Allparts and WD, depending on who has the better price or what's in/out of stock:http://www.allparts.uk.com/
the spares box at work 8)
Does this actually make much difference? I've read elsewhere that the effect on tone is marginal. But having said that, the stock tone pots on my 79 335 are absolute pants. They just add muffle on anything below 9 to my ears.