Unplugging the IAC got it through the MOT. This give me some time to think about it more. With IAC unplugged it ticks over at around 500rpm until the engine warms up and then it idles at around 1300.

Will running with the IAC unplugged cause any long term damage?

Thanks Roger - at least I am not alone!! I also tried disconnecting the MAF sensor, and have disconnected the battery, shorted the positive and negative feeds to the car together for a few minutes (I read this somewhere else and I presume this resets the ECU - thought it worth a try). I won't be abl...

Help please: My 850R (Auto) failed the MOT as the tester was unable to maintain a "fast idle". When the engine is running it idles at around 1100 rpm, but it is impossible to get it maintain steady revs with the accelerator pressed. It gradually rises to where you need it then carries on r...