There are 3 wires coming out of the brake lights, does this mean they are both brake and tail lights? Obviously when brake pedal is pushed they brighten up?

well you could take the cover off (I think a crosshead screwdriver would help) and have a look

It's a single buld inside, same as Land Rover Defender

and if you take the bulb out, does it have one or two connections on the base?
or count the bulb filaments

I shall upload a picture of the inside tomorrow

Series Landrover lamps they take standard 5/21 watt double filament off set pin stop-tail bulbs, Bulb ref. type 380.
Black wire is earth, red wire 5 watt tail, green wire 21 watt stop light.

[Edited on 3/3/15 by britishtrident]

Put the black cable on the negative terminal of a battery try each of the other cables on the positive. I think red is sidelight and green brake.

Cheers guys. Will try tomorrow