Seems to be ok now, it passed the MOT and i've been thrashing it all weekend so now it's come good, I speculate that it was just damn cold & damp, having not been driven properly for a long time. I did find one other wiring fault which has now been fixed as well, so it is 100%.
It's bloody lively now, and with the cold/damp roads at the weekend up here it hangs the arse out as soon as it comes on boost (there's no gradual drift sideways), box sounds ace too!!!!Feels dangerous to drive in the cold weather with the red frost light on, just the way it should be.