TVR Tuscan S tail lights

[cliffordwhitehea]

It might sound daft but can anyone help me out, the offside tail light has gone and i only want to replace the bulb, on removing the cover from the light the housing for the bulb is visible but I cant get it off without fear of breaking the unit, ive tried to twist it with a pair of grips but its very tight, it doesnt seem to pull put and when you twist it the hole light moves, the light its self doesnt look to have any sort of seal around it and i fear using more force will either damage the light of the body of the car?? Has anyone got any advise for what should be a simple job??
Thanks
Cliff