A friend of mine recently attended a chocolate party run by a company called Choqui (i think they're at choqui.co.uk or chocolatesandsweets.co.uk - I'm not sure which address is for the parties)

Apparently the chocolates were all made by the party host and were amazing. I've also heard of chocoholcs doing parties but I think they are a bit "woolworths" in their quality - all bought-in.