I must say that if you want to be brave and remove the ford blinkers, theres a load of better track ready cars to be had than the zetec S. Ive done trackdays for 10 years now and have had all sorts of fords, and spent many a thousand on the way..
Hence now im driving a shitbox of a primera GT - I had enough of chasing bulshit power figures and am having as much fun in my flying turd as i did in cars owing me thousands.
The essence if your sharing with mates, is keep it simple, know your limits and dont be too upset if one of you bins it big style.
If your insistant of ford, the RS2000 would be a better bet IMO over the fiesta, cos although the fiesta handle exceptionally well, you'll soon be missing the extra grunt on the faster bits that the 2k will give you. Plus the 2k will be cheaper to buy in the first place.
Ive got a good mate who tracks a Mk5 rs2000 and its a real strong car, and we have many a laugh on trackdays, cos the 2 cars are fairly evenly matched.