Sort of an update.
Spoke to Mazda at length today, and they have admitted there is a problem. They went on to say their technicians are looking into it but at present there seems to be "No Fix"
So I've made all these visits to have the unit assessed then replaced, and have been in dispute with both Mazda & my dealership, only to learn at this stage there is no solution.
Regretfully Mazda customer service are not being very helpful. They tell me they are looking into the matter, and they will log a new case number, but will take 3 to 5 working days to get onto their system, what they don't tell me however is what they are going to do about it!
Next time I replace my car, I will go back to a stand-alone version.
Alex