Drill holes and the condensation will be far worse!!
I had this problem, its the gasket seals, I took the backs off the lights (inside the wheel arches, the ones you take off to change the bulbs) I then thoroughly dried out the lights using a hairdryer!!, watch for the water that sits in the tray at the bottom, you will see what I mean when you are doing it,that bit is the hard one to get rid of, you can if you are brave get rid of the worst of this with a straw!!pryor to this I bought new rubber gaskets (came with the covers too) put them back on, no condensation whatsoever. total cost about £18