After much testing and agonising I sent the throttle body to BBA who said they could find no fault and that the TPS was ok. Even though both tracks of the TPS had looked ok to me on the scope I asked them to replace it. When I connected it back up I immediately knew it was going to work as it initialised through full travel and parked at idle position.
I'm so annoyed as if the TPS was available I would have put one on straight away.

Shaun.