Google Delia Smith's lemon curd recipe
OK - Here it is!
Use a bain marie, not the saucepan she suggests - you'll thank me for that tip come the washing up. If you keep bantams (and you should!) you'll need six bantam eggs instead of the four large eggs the sainted Delia proposes.
This is a quick and easy recipe - but it will put you off the shop bought stuff forever - it produces wonderful results.