Correct, you cannot run Punto GT discs and Cinq calipers. The calipers are all of a closed back design, so they won't go round the Punto disc.
I decided that I wanted vented discs. I bought a set of Punto discs and calipers. They fitted perfectly without modification, but I could not get my 13 inch wheels over them. I could not get 14 inch off road tyres in a low enough profile, so I looked at the alternatives, hence the Uno tubo set up on the car.
Remember through all of this that I used the car off road and I go through brakes at a furious rate. I have never fitted 'fast road' kit like your talking about. I went for the best basic set up I could get so that I could buy replacement discs over the counter at my local factors without having to go to a specialist, or wait for mail order
I think I have different priorities when it come to choosing.
Cheers
D