According to my Bently manual 216 f is the highest acceptable range.  So, yours is hot, but not out of range.

In the troubleshooting section it lists that if you all else is functioning, and the coolant level is steady, the problem may be electrical - radiator fan, instrument/sensor failure, cluster failure.  I hope your mechanic would have checked all of that, but you might want to go over it again.

I pretty much accepted that my Dash Gauge isn't reading the temperture correctly.  The needle is very steady once it settles in the notch past center and the car runs great.  My digital gauge shows a 204-206 degrees and a lot of people are telling me that is normal for the TT.  So I will ignore the dash gauge and go by my digital Temp Gauge.