Engine Running Hot

During my trip to the Nurburgring at the beginning of May I had a worrying temperature guage reading for pretty much the whole trip.On my return I decided to check the cooling system to find the fault.I drained the coolant as per the instruction at the excellent Clark's Garage website before removing the hoses to get access to the thermostat.The thermostat is quite tricky to remove due to the position inside the water pump.A good set of circlip pliers are needed to remove the clip which holds it.I bought this set from Amazon: Draper Pliers
but they turned out to be wrong for the job, the jaws didn't open wide enough to get the nose into the holes of the circlip so I went to Halfords and picked up a set of these:
Halfords Pliers
They did the job well and the thermostat was out within ten minutes. I wanted to check the temperature rating on the 'stat and it was stamped 80 degrees however I was not happy with it being stamped 'Calorstat Made in France' so I ordered a new one from Porsche.
Looking at them side by side you can see a big difference in the parts.Porsche part is on the right.

Installation was simple however I noticed that there was some play between the new thermostat and the circlip.Some advice from PCGB forum confirmed the need for a shim.Turns out there are updated water pumps (which mine is) which have a larger gap and require the shim.
I replaced the coolant and bled the system, started her up and ran at idle until the guage started climbing.
At midway between the 80 and 100 marks the fan switched on and the gauge went down to just below the 80 degree mark.

Success!!!! No more driving with the heaters on full and the windows down