Great, thanks for the advice. I'll try to pull the belts of tomorrow.

On another issue, I noticed that the idle appeared low. What should it sit at. Mines at 500ish. I was driving today when going round a car park on tickover when the car stalled due to low revs and me turning the steering combined caught it enough to cut out.

Seems that when slowing down the revs drop of and the car just catches them on time to stop it stalling. This time it missed it.

Any thoughts on where to look first?

I know an indie BMW guy remapped it previously to stock settings so perhaps just get it redone?