To avoid expensive dealership's trying to trace a fault I decided to invest in a Foxwell NT510 BMW/Mini multi system scanner, and this confirmed that the brake vacuum sensor was showing a error code 4AFA, checking online it looks like part No.34336786746 is required looking at parts list this sensor was fitted on vehicles with stop start across both BMW and Mini with differing part numbers for different years, but they all look like they are fit to the vacuum reservoir the same.
Whilst this link is a Foreign site it shows the part and location.
Does anyone know if its possible to fit without taking the vacuum reservoir off the car, looking pictures of the part its just looks like a serrated push fit connection into the vacuum tank, my guess is they don't pull out easy or push in that easy as space don't allow for large hands.
Information to those that have stop start when this sensor fails you just get a warning of stop/start failure on the dash when the vehicle would normally stop start everything else works normally apart from stop start feature, whilst you can survive without this feature its just annoying this warning message keeps occurring.
So if anyone knows a easy way of fitting a new brake vacuum sensor it would be appreciated.