I waited there, and no they weren't interested in a test drive after all. None of their promised senior staff were available. And their investigation was nothing more than a visual inspection on the ramp, with the camera pointing to a Mercedes bulletin saying I need winter tyres. They did give me a letter by Mercedes UK addressed to myself (amazing that they had the time to get that so quickly

) highlighting that this is not a safety issue, merely a comfort issue. Well at least they recognise that part

But ahem that is it, there is no problem with the car. And infuriatingly they had to audacity to tell me when this occurs. Funny that as that doesn't match with this owners experience. And they can do and diagnose that all remotely. It is a bloody miracle.
So cancel it, I would if I hand't bought this already.