I had water inside my boot when I first had the car, the carpet lining was dry but there was water in the tyrewell, and a fair bit too.
I checked for leaks but couldnt see anything, eventually after weeks of searching by myself and the dealers, I worked out that it was condensation from having an alloy spare wheel in the tyrewell !
I found that the exhausts rear box sits very close to wall of the tyrewell and in cold weather the warmth coming through the tyrewell wall warms up the alloy on the spare, so starting and stopping of the engine was causing the alloy to get warm and cold, therefor getting condensation around it, after a while a pool of water was sitting under the spare.
Warmth transferring through from the exhaust box meeting big cold spare alloy wheel = condensation.
After a trip in your Z feel the side wall of the tyrewell, you'll be surprised how much heat comes through the wall, in fact theres a heat shield mat stuck to the metal floor of the boot because of the heat coming through, so Peugeot know about heat transfer within the boot/tyrewell.
I dried everything out and wrapped the alloy spare in a cotton blanket and hey presto, no more condensation or water in the tyre well. :thumbup:
As for your lights, well mine are ok, no condensation, however my old Vauxhall Astra suffered terribly from the rear lights getting condensated, I took it back countless times to the dealers and had complete new sets fitted and seals a number of times, but it always reoccurred.
Vauxhall even modified the seals around the lights and anounced a call back for certain models, but they still couldnt solve the condensation. If I remember correctly the explanation was something like, "plastic lens's create and hold more warmth from the bulbs hence causing condensation on damp/wet days, and depending on the actual shape of the lens, some cars suffered worse than others, ie the Astra H".
Vauxhall finally admitted defeat with their Astra H and actually made the top of the lens on newer models slightly opaque so that any condensation was not so apparant, basically still having the problem but now masking it from view. :roll: