Had this problem since summer, seems to be getting slightly worse as weather gets colder. Symptoms are going along quite OK, then suddenly engine seems to lose power and you notice speedo has dropped to zero. If you have to come to a stop it will stall. Restarting seems to cure it. It can just disappear and you'll quite OK for rest of trip. Just did 600 mile round trip to Lakes district from south London and it never missed beat. Current mileage just over 57,000. Most miles now are crap short journeys in 'lovely' south London traffic jams.
Any suggestions?
Martin J.