Nearly there
Woke up early and set to work while the car was still frosted up. This machine is never far from my thoughts, it's become a puzzle I must solve. Perhaps I'm going a bit mental.
Driveshaft finally off, though ended up taking off the strut to get clearance. I've got a PDF of the factory Alfa workshop manual (complete with dodgy translations), it reckons you can take the shaft off by only removing 1 bolt from the strut but nope. Should have just undone the bottom balljoint.
New thermostat on, with £15 of new hoseclips from Halfords.
Exhaust back on, but unable to test as in middle of oil change. Didn't take long for rain to stop my obsessive fun.