Why not get the cosworth kit for the fiesta? They look like mini escort cosworths...more or less...I seen a decent one a couple of years ago in blue.
The reason I was saying you mays well get a real one is...
Getting a full decent kit is going to cost over a grand, it's not just the vents, front splitter and tail, the cosworth has blistered arches, so that means you're going to have to get them fitted and sprayed...and maybe smoothed, then you've got the alloys on top of that, (and the spacers for the wheels). That's probably about £3000-4000 already, (don't forget some disk-brakes for the back wheels too, cossies didn't have drums!), then all the performance mods will be ££££££'s! I'd invest your money in your fiesta, it's already taking shape with some nice looking alloys, plus there's far more performance mods out for the fiesta.
Make a cosworth-a-like if ya wanna, but I'm fed up of racing those "special edition" 1.4 Cosworths off the lights.
I have to agree though the insurance on cosworths is CRAZY, I got quoted almost £3000 a year on a standard one, frig that! They're not that good, a sorted Subaru Impreza Classic can out-corner, and out-perform one for cheap as chips money, the only thing that special about the cosworths are the engines in my opinion.