tich. It happen to me last year, exactly the same. Mine was an intermittent electrical problem that they half identified, but saying that if it wasn't that, I would still have to pay for the £400 part and the labour. They spent a long time "testing" everything over around 2 months, and when I decided this was going nowhere, took it home with a £480. bill paid for their efforts:question::question:
I took it to a chap in Whitley Bay, took one look at it and said, I can fix that, lifted the cowl off, pulled the flywheel off expossing the stator, identified the the stator as "shot", fitted a second hand one, started it up, and wow! job done, all in the space of 90 minutes.
So I would personally give them a wide birth and go elsewhere.