In article ,
Adam Aglionby writes:

Can also fit a 300W lamp in a 500W fitting , they`re the same length.

And 200W, but they're harder to find.

There are also energy saving versions -- 375W instead of 500W,
and 225W instead of 300W. These have an IR reflective coating
on the inside of the tube to reflect heat back on to the filament
to enable it to reach the same temperature by using (and wasting)
less power, whilst giving off same amount of light. These are
also hard to find -- I have bought them in B&Q, but they don't
often have them in stock. (I suspect the problem here is that
people interested in energy efficiency wouldn't use halogens in
the first place, so there's a rather small market interested in
energy saving halogens.)

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]