Finally back on the car. Found the reason why one of the bracket mount holes was threaded, which was the reason for going through all this pain in the first place. The guy who originally did this conversion didn't grind enough off the trailing arm...so the caliper was hitting up against it. I don't know how he managed to get the buggered bolt in. They are both immovable objects. But he did and threaded the mount hole in the process.
Took me 5mins with an angle grinder to take off the couple of mm's required for proper clearance. Calipers now bolt on perfectly. Sorry for the pics. They're a bit blurry.
Spent an hour or so bleeding all 4 corners today with the help of my missus. One thing i've noticed already is the handbrake is working a lot nicer. Both sides seem to be grabbing equally rather than before when i was only getting one side to grip.
Also found a hairline crack in the bottom tank of the radiator that was seeping coolant very slowly. So buggered if i'm going to take out the radiator for just that, a bit of putty should hold it for a while until i decide to reco. the radiator again.
I'll take her for a spin tomorrow. It's been a while so should be good.