I resistance checked the crankshaft position sensor, it checked out fine with 845 ohms.
I then checked the air flow pot as you recommended saumil, at idle in drive I get almost bang on 0.7V, fluctuating around 0.71 as the idle is slightly unsteady. As the revs are raised the voltage slowly raises with them, no jumps at all. I went upto 3500rpm, way beyond my problem zone.
I will check the throttle valve switch next for completeness. Where do I go from here?! Is the TDC sensor important?