[Andymharrison]

Well I finally got a chance to look at this. The drivers side unit, the old one, does have a black rubber seal around the edge but with it off the car for a closer look it is definitely not original.

A previous owner must have had an issue with that unit, it does have a small crack that has been sealed with some kind of glass tape. Its been like it for longer than the 5 years I've had the car and showing no signs of leaking so I've always left it alone.

So it looks as though the condensation in my new unit has a different source and nothing is missing after all.

Time to bring it indoors for a few hours in the food dehydrator, next time the wife is out!, before investigating the bulb holders.