Good morning and welcome Brian,
Sorry to hear of your issue.
It seems - quite fairly - that your trusted local garage is not best equipped to sort out this issue, and may even be suggesting work beyond requirement, obviously not to get you to spend money with them, since they have told you they ideally don’t want to try to sort it.
If it were mine:-
I would be doing a search for a localish trusted independent VAG specialist and seeking advice on what needs doing ( and not asking how much it will cost to remove the engine). I would want to be talking with the principal there, and outlining the initial issue, and what has been done so far, and see what their recommendation is from here. Obviously you will have studied their reviews before engaging with them, and taking advice from local VAG owners if possible.
Perhaps you could let us know how you get on Brian.
Kind regards,
Gareth.
p.s. I was going to suggest placing another post asking for recommendation for independents in your area, but you state your location as a vague U.K., so difficult.
Worth posting however, and specifying your area.