Dimming side lights when signalling

Can anyone tell me where the earth points are?
I ve spotted the one in the boot and that appears tight.
Any others to check for the above problem? Only appears to happen when side lights are on, not when braking and indicating.
Thanks
Gary.

There's most of the earthing points listed on THIS thread.

Thanks for that, I'll have a look. Maybe it will pass the MOT in time for the next NW meet?

Turned out to be the multiplug in the back of the light cluster wasnt a tight fit, i wedged a piece of card in and it works fine now...