Booked in for a look on Monday. Fuel hose getting done. Said they had no knowledge of a rear wiper scrub fault and they couldnt think of anything causing vibration rumble... thank goodness for macanowners club!
Get your dealer to search their internal database and they will find a Service Note which describes the problem and corresponding fix for the rear wiper rubbing issue. It's not out as a recall as it's not affecting every car but my SD (first registered March 2015) which I have just bought had this problem and is now fixed.