Had another dig at it this morning,
checked the relay, that was all fine but had a new one here so swapped it to be sure.
had a bit of a play around, manually wound the eccentric shaft to half way through its movement and then tried to run the self calibration, and surprisingly...... it moved..... but only in one direction only and would not do the full sweep!
decided that it was time to have a look at the sensor, so pulled it off, pulled the back out of it and what would you know, it’s full of oil like their usual failures are!
have just ordered a new sensor, valvetronic motor, gaskets and seals to chuck put it all back together and hopefully the issue will be solved!