Rear light help!

Hi I've got a 300 series Disco
On the nearside the rear lights (not indicators,brakes or reversing) have stopped working (and I believe may have taken out the trailer sights as well). Having got into the light cluster (a real sod with the rear seats in them!) and checked the circuit using a multi-meter. There is continuity from the connector. The bulb is OK. The rear light in the bumper also doesn't work either. I checked that the circuit has continuity and the bulb is OK. I've checked the fuse, that was OK (obviously because I'd checked the continuity -derrr) but still swapped it. Checked the voltage but the amount coming through seemed to be ridiculously low, although the engine was off.

Any ideas? Anyone come across this problem before?

Thanks

Andy

only seen summat like it once before. a wire had been chaffed/corroded and was giving high resistance. hence the low voltage at the light socket end.