Crankcase seals replaced sounds onimous, surely that would have necessitated draining the sump of oil?An update on my specific experience: diagnosed as faulty thermostat and they also replaced thermostat seals and crankcase seals. Now running well again. Audi Camberley got me into an A7 55 TFSI for 1.5 days, and an A5 2.0TDI S-Line for 1.5 days whilst mine was being sorted out. They also topped up the engine oil alongside the other work. All in all a frustration but they dealt with it well
Further update, went out on another run, temp climbed one notch above 90, orange engine management light came on this time. Noticed that even on max the air coming out of the heater was not that hot. Got home and the fans were running fast but the whole engine bay felt cold. Indicated oil temperature was about 60. The expansion tank for the coolant felt tepid at best. The only indication of any form of 'overheating' is the temp gauge.
Perhaps @D-Lat would be good enough to change the title to start stop system fault - Thermostat. As I understand it whenever the ECU detects 'anything' out of normal operating parameters it switches the start stop system off - so likely this warning is a precursor to multiple issues.