Ok, we have more news this morning.
Fuel filter is going to be replaced, but the fault seems to be electrical.
1) If the dbw throttle is unplugged, and the car started, then the car will sit and idle quite happily for as long as you like and sounds fine. No missing etc.
2) Plug the throttle back in while its running and it dies immediately.
3) If the fault codes are cleared it seems to run like a bag of bones until they are stored again. Then next time of running, and thereafter, it seems to run ok again.
4) Manual opening of the throttle does not increase revs, but garage man believes that might be because other parts of the system are not expecting it to be opened??
The garage are wanting to replace the throttle body assy. as they say they have tested the connector / wiring. This is a non returnable part so if they go ahead and order it and it makes no improvement then its still going to cost me nearly £300.
Can anyone help me and tell me if you run the car with the throttle unplugged, and plug it back in, does it still run? Also, if you manually open throttle with it unplugged, does it increase rpm??
I would REALLY appreciate your help on this one.