The official line from the official MoT test manual on the matter is: "Where items are present in the driver’s view (such as a sat nav, air freshener etc) that would justify a Reason for Rejection, the tester may, at their discretion, remove the items prior to the inspection. This fact should be noted on an Advisory Notice."

So MoT failures because of such items are extremely unlikely. If you look at our recently updated MoT files you'll find the most common failure items within the 'driver's view of the road' category are windscreen wipers and washers.