I have a 2005 XK8 and the headlights have condensation inside. My dealer claims that this is a common problem and will go as the headlights are used.
Is this true because it seems to be getting worse?

Hi Nigel, welcome to the forum.
I have a MY2000 XK8 and had the same problem, particularly on the near side light. Last spring I just could not get rid of the condensation at all.
I bought the 2 T-pieces to fit them, but found my hands just did not seem to be designed to get into all the nooks and crannies to remove the light units.
Went to my preferred dealer, Guy Salmon Coventry (ex TWR), who told me my headlight did not have the required 'blind spigots' which you need fot the T-pieces, so they just drilled a hole into the body, which they said was their normal method of fixing the problem and it 'usually' works. (did not charge me, all part of customer service they said

)
Well, although it still mists up when I wash the car, it disappears quite quickly once I am on the road.
Hope you can get it fixed soon.