So the story continues... (if anyone interested!)
I emailed customer services and threatened to get the issue investigated and resolved independently -at their expense. They soon responded accepting "possible mis-diagnosis" and suggesting booking into another dealer for a second opinion.
So I arranged for VW Worcester to investigate- I must say this dealership seems a much better run outfit than the 3 others I have had dealings with. Service manager took interest and gave me confidence they'd investigate properly. They score well on google reviews, which shows that, at the very least, they give a sh1t.
The master tech didn't feel there's any issue with the clutch- he thought the pedal feel was fine, bite point was good, no slip on road testing and no oil underneath the transmission on inspection.
Gear linkages checked and adjusted- he did feel they needed a fair degree of adjustment and was confident this would solve the problem.
They did cold test this morning and felt gears working ok.
I've had the car back. Reverse going in ok, but first now very reluctant to go in!
I'm taking it back to them next week, when hopefully the problem will be resolved.
I'm pretty confident now that there isn't a clutch issue, and that some fine tuning of the linkages will sort it out.
( and obviously happy that I haven't had to needlessly shell out £1000 - or £1700 if flywheel replaced too).
Incidentally an interesting discrepancy in brake pads checks between the first and second garages - 40/50% and 10% respectively!