ooh, you've reminded me.  I was going to look at switching the brake and fog
lights on the disco this morning.  Done this to a couple of things, I reckon
it makes sense - make the rear fog lamps into brake lamps and vice versa.
That way, rear fogs are just bright rear lamps, which is what you want, and
brake lights are a separate light which comes on when braking - if you've
got the rear fogs on, especially, brake lights can get overlooked, whereas
another light coming on, equally bright, will get more easily noticed.
Assuming the mutleyplugs come apart, it's just a case of swapping a couple
of pins, if not, it has to be done by cutting and joining wires, which is
less than optimal.  

Mind, the other thing I'm contemplating is modifying the rear lamp clusters
to use arrays of LEDS built in behind the lenses :-)

Thanks Tim,
Brom.