Re: GTV running hot
There are 2 speeds for the engine fan ( apparently), it sounds like yours could only be working on one. I had the exact same symptoms as you and it was a combination of fan only working on one speed, so it could not keep the engine temperature under control and a knackered rad. Both have now been cured, ( new rad and fan sorted) and I rarely see the temperature move above 100, even in hot weather stuck in traffic.
You will probably find the performance is pants when your engine is running as hot as you have expereinced.
I would recommend you get the fan looked at first, if thats ok,then my money is on you needing a new rad, which should not cost more than £200 fitted.