hi mate sorry to hear about the car.
when i first got my mk3 it would cut out randomly and sometimes in really bad places lol
i took it to the garage and the couldnt find anythin wrong with it, i tried alsorts,changin the battery and things like that
but it kept cutting out and it started to get on my nerves.
after the car cut out it wouldnt sart up again but after a few hours it would start up fine

so i took it back to the garage and told them what happens and they took it for a drive for a while until the car cut out then they checked under the bonnet and it was the distributer it had a split in plastic cover that opened up when the engine heated up

so i got a new one fitted and its never happened since
so......... maybe its something like that?
hope that helps any, let us know how you get on