Martin Angove wrote:
... If I had the chance of working on a building while
being filmed, I wouldn't offer any special deals because if you get on
camera at all, it's for two or three seconds, they usually say something
like "and the bill for the electrics is twice as high as expected" and
even if your logo is emblazoned across all available area of your shirt,
it's rarely seen for long enough or clear enough to make an impact.

However the value possibly lies not in the advertising on GD itself,
which as you say is negligible, but in the press release you send to
your local papers "Local tradesman featured on telly programme", etc.

Owain