E320 Headlight problem

First time user - Hi I changed the bulb in my headlight - very difficult to get access without dismantling air intake etc. Despite ensuring rear part was properly sealed when finished, I'm getting enormous amounts of condensation. It is about 2cm deep after a couple of weeks and returns after I dry it out (using small pieces of paper towel on a wire) - takes about half an hour. Any ideas what is causing this and/or a cure? Thank you R&BW Jack Lavety ABERDEEN end ============================