indeed i did. i wired in a potentiometer, a variable resistor and linked this into the lighting circuit.
if you go down to your friendly maplins store and buy a potentiometer (i bought 10k, though a small value would probably work better as i have 50% adjustable variation with no light whatsoever) and wire it into your LED light wire for the gauges.
check here mate for different ones, the 4k7 should be sufficient.
http://www.maplin.co.uk/search?criteria=potentiometer
when you get it, check the response with a volt meter, make sure you wire it the correct way, as you will typically want to dim the light down when you turn it auto clockwise (as most stuff in industry works on a voltageincrease-clockwise function). you know what i mean when you wire it.
need anymore help just ask mate