Polywave,

Yeah the dew point thing happens wherever there is air. Yep, even in the North West! :wink:

I think the Nitrogen plan would work fine - let's face it, 80% of air is nitrogen anyway! Whatever they use, it would have to be moisture free and done in a dry atmosphere.

I've had a think about it and I wonder if they could make the "outer" part of the unit a sealed area rather than the whole unit, thus allowing access to the bulb area (so that exchanges can be made). I haven't looked at the unit itself in much detail - a job for tomorrow, I think!