Condensation in rear light cluster housing

Apologies if this is not strictly a very technical issue, but there is condensation in my near-side rear light cluster housing.  I imagine this can undermine the electrics and certainly the bulbs in that cluster.  Should I be looking to replace the whole configuration, or should I be looking to get a new seal for it?

FYI: I have the silver PT Cruiser Limited CRD 5-door 2007 - is.gd/My57PT

I only joined yesterday, so I have to wait another six days before I can post proper links.

My left had side light also fills up with condensation which is worse when hitting puddles and it splashes into the rear wheel arch.
Due to the cost of these light units I will be taking mine off and sealing the edges of the cluster with silicon for now.