Been away for the last 5 weeks so not been able to get on to see any replies, so thanks for the previous advice. I barely drive it, as I work away 6 months of the year, and when I do drive it I'm not a Sunday driver but I'm not thrashing it either.
Before the EPC light was on and on the code reader it showed 3 occurrences of a problem at 4000rpm with a code of P0321/000801 - Engine Speed Sensor (G28): implausible signal. This would only read from the engine management though, and not from the cambus (different serial ports) I'm not sure if this is normal or not? Anyway, the engine light cleared.
Just given it another go and it seems the problem comes in at 4500rpm, doesn't matter how hard or soft you accelerate, it bounces right back as soon as you reach 4500rpm and seems like its misfiring. There's no EPC light on now although the Exhaust system fault light is on (possibly from misfiring?)
The G28 sensor is about £50 I think but before I go out and spend money on that does anyone have experience of a similar problem, or have any other ideas?
Cheers