So, here's an attempt to square the circle on this thread.
The good news is that the brakes are on the car, and they're good. Very good. It's not quite the same as jumping from the Fiat in to my boring, modern, Audi A4 estate, but it's not far off and it's noticeably much, much more efficient at stopping.
The biggest difference is the firmness of the pedal, which feels much more like a modern car. The drum brakes felt pretty spongy in comparison (when I've driven it for a few days running I almost put myself through the windscreen when I get back in to a modern car)! But now the pedal is rock solid from the first millimetre, like a modern car I guess.
It wasn't quite as easy as a straight swap, and there was some fettling involved (which I think I'm learning is pretty much always the case with classics). Nothing too dramatic:
1 - My wheel bolts were unusually long and were catching on the discs. So they had to cut those down to fit.
2 - The plate that the callipers mount to didn't have any fixing bolts. They didn't have any kicking around the workshop and had to quickly source/buy some.
3 - They also needed to add some washers/spacers between the mounting plate and the assembly to stop some additional catching (I assume on the hub or the disc).
Nothing too dramatic, but enough to make an alleged 2 hour home garage job a weekend long head scratcher.
The not so good news is that the mod has resurrected an old problem of mine, and that's tyre rub at the front of the wheel arches when turning (especially at speed). My arches have been fettled twice before to scavenge a few millimetres, firstly to account for the alloys and secondly the Abarth suspension.
It's always baffled me, but Middle Barton diagnosed the reason last year. At some stage in the car's history it's had a front end shunt. Nothing serious, but enough to just push the bottom of the front panel inwards and, with it, the front of the arches.
MBG's panel beater managed to pull it out last year as a temporary fix, claiming back just enough clearance for it not to be an issue, and I never got around to getting it done properly. Now that this mod has reclaimed those few millimetres it's time to visit a good quality panel beater and give myself plenty of clearance in those arches!
To end on a high note, it flew through the MoT!