Audi S3 2014.
Came across Revtronic amongst google searches when Audi main dealer quoted circa £3k to repair (or rather replace MMI unit in glovebox) due to intermittent sound or no sound despite everything else working ok. Spoke to Revtronic over the phone beforehand and they quickly identified what the likely cause of the problem was. Bit twitchy about sending unit in post but having done so via tracked Royal Mail on the Thursday the unit was repaired and back in the car working on the Tuesday - 3wd's. Superb work. All done with 12 month guarantee. Puts Audi to shame..!!