When I stayed down that way for a few months, driving around the Ely, March,Cambridge etc area I had one of my lexus ls400s, nice roads to blast down, very fast and windy, not to many tight corners,very flat so you dont need so much grunt.
I could see a TT running out of steam on those roads, they're more of a point and squirt kind of car.
I would think more of an E class or 5 series would be a good car down there if you are planning to use a car to its potential.
Where I live my car is much to powerful for the roads, they are very twisty and short, a smaller lower powered car would have been more suited. My old SL350 was actually better for the roads than my sl63 is, I did look at a few porsche and toyed with the idea of Bentley and Aston.
But then I bought the car I wanted not necessary the best car for the purpose.