Seems to seize at about 2C.
When I bought the bike (complete with shiny new MOT ticket), the front brake was almost adequate if I never went over 30 - the rear brake only worked if I stood on the pedal and jumped up & down, then stayed on until the pads wore clear. The rear brake has had new seals top & bottom, cleaning up the corrosion took some skill not to remove too much metal, loads of silicone grease on re-assembly is a given. The front brake has had new master cylinder seals and DOT5 fluid, I worked the calliper pistons in & out with some fresh silicone grease - the light was fading by the time I'd fitted the new tyre. The new seals are in a drawer ready to go in and it'll probably be less of a bastard once that's done.
When they work, they're excellent, but 'cos they're shite in the long term I'd seriously consider different wheels/brakes/forks.
Or an Alfa Romeo. Inboard discs are great, keeps them away from the road grit, salt and shite. Not so good for cooling though ... Paul.
Not so lovely when they were new, luckily the first owner got modified cam chain tensioners under warranty. The service log also shows it had a replacement set of carbs early on in life.