According to Claude-France Dubois, the finest chocolatier in all of France is to be found at a place in Brest called Histoire du Chocolat. The upside, though, is that you'll end up with your actual, handmade, superposh French chocolate. I hear that its extra-crunchy Florentines are particularly delicious. Don't worry if you can't speak French, the text on the above site is all in English.
Delivery takes just under a week.
If it's Easter eggs you're after, though, you'll have to stick to British chocolatiers, such as the ever-reliable Thorntons. For something a little more unusual, you might try holdsworthchocolates.co.uk. I made it on the eighth attempt. It does smaller ones for as little as 5, plus tiny ones for Easter-egg hunts at 2.50 for 4oz. Frankly, after all that chomping in the name of research, I'm totally chocolated out.