Rear reflectors and number plate lamps:

All vehicles  (except those not fitted with any front or rear position lamps) must have two red reflectors facing the rear, fitted at the same height and same distance in from each side. Reflective tape is not an acceptable substitute and the approval marking is not part of the test.

At least 50% of each reflector must be visible from the rear. This takes into account structural features of the vehicle i.e security vehicles, off-roaders etc.

Number plate lights must illuminate the plate and the bulbs can be of any colour. The lamp must not flicker when tapped but could show a white light to the rear (i.e cover missing). This is specifically exempted in the Lighting Regs, presumably because it's almost impossible to provide a light to the plate which cannot be seen from every angle, i.e vehicles with a very high driving position like HGV's or vehicles approaching from the side. All bulbs must light.