Does it have a PRT Thermostat fiitted? ie a plastic thermostat unit between the engine and the firewall?
And if so have they fitted a standard thermostat in addition?
Have you renewed the coolant pressure cap with a good oem new one?
I recently replaced the pressure cap, as a service item, with a new oem one. Next day I experienced bubbling up in the expansion tank and over heating. The expansion tank was almost full to the top when I looked after a run! Changed the cap back to the old one and problem has gone away! All back to normal
So even a new OEM cap can be faulty...