My rear fog light goes on and off automatically whilst driving and when I try and switch the fog lights on, it does work. I have changed the bulb and switch but no joy.

Anyone have any ideas? Thanks.

Sounds like a short in the wiring.  Could be anywhere between the switch, fusebox and lightbulb.  Maybe one for an auto-electrician unfortunately.

Thanks for the info Tom. The heater matrix went a few weeks ago and the garage had to remove the whole dashboard to replace it. It started playing up soon after. Do you think they might have knocked something?

12 hours ago, Maunder said:

Thanks for the info Tom. The heater matrix went a few weeks ago and the garage had to remove the whole dashboard to replace it. It started playing up soon after. Do you think they might have knocked something?

Does sound a possibility. I'd take it back for them to check as removal of the fog light switch is a lot easier than whole dash removal! You've been very unlucky to have the whole heater matrix fail on such a relatively new car. Usually it's cars of my generation that fail...

14 hours ago, Maunder said:

Thanks for the info Tom. The heater matrix went a few weeks ago and the garage had to remove the whole dashboard to replace it. It started playing up soon after. Do you think they might have knocked something?

Must admit it seems unlikely with just one fault.  If they'd knocked a multiplug or trapped some wiring I'd expect multiple faults.

Same with the GEM/BCM, if there were multiple faults I'd suspect that but with only one it doesn't seem likely.

It really does just need proper electrical tests done to work out where the short is as quickly as possible with minimal dismantling.

Does it need to be a specific type of mechanic? or should most be able to do the electrical test?

11 hours ago, Maunder said:

Does it need to be a specific type of mechanic? or should most be able to do the electrical test?

Any competent AutoSpark (car electrician)should be able to do it - that's their bread & butter...