Thanks for the input everyone. The dust is all over. It's a thin film, but I am pretty fussy about such things. I would say that in its 12 tears, it is a reasonable amount and not excessive. A clean will sort the issue. As far as cleaning the lamp reflector, I have been told a good quality make up brush or a forensic brush work well.
I refuse to be beaten by this bloody thing. The oven could work, but I would prefer to use an industrial one with a digital temp sensor rather that the random dial on my SMEG one at home...
Acetone dissolves glue, but I fear this could damage the reflector if it gets in there. What a pain in the arse, but its £350'sh for a replacement, aye right