Yes, that does make sense, and I assumed that had something to do with the problem. But turning the traffic info setting off and on and turning the radio off and on again didn't sort it. Who knows!

Well, it passed the MOT! Bonus.

 

The rear brakes are only an advisory (corroded disks, not excessively pitted) it seems as braking force at the back is still adequate. Might even dismantle the rear brakes myself and see if I can get the sliders moving properly, should stop the disks from corroding much more.

 

I treated the car to a re-gas of the aircon while I was there too.