In the end, my nerve cracked, and I called them at 4pm, to be told “We’ve just finished, and it’s ready for collection”.
Walked over there and was told “Yes, we could see what you meant about the judder, but we went ahead with the service, changed the spark plugs and fuel filters and cleaned the fuel line; and the problem seems to have gone. It’s passed the MOT, and we think it is fine, now, but if you have any further problems, give us a call”.
In the end the service and MOT cost me just 200 quid, and the car is humming like a well oiled machine – which I guess it is.
So with any luck, it *is* going to reach its 10th birthday next year.