Bit of a hiccup. I put on the master cyclinder, calipers etcetera, bled it all with the old pads in. Got the front wheel off after a bit of brute forcery with a braker bar. Got the discs off ready to put the new ones on. Got out the new ones and they dont fit. They have 6 holes and the old ones 5 and there is no way of getting them to line up. Emailed the supplier, just an automated response so far. Put it back together with the old discs and pads (keeping the new pads for when I actually get the discs) to test the feel of the brakes. Getting the axle back in was a bitch of a job and required prodigious use of the heavy hammer and a block of wood. Still a bit of lever travel / softness at the beginning of braking but they actually bite quite a bit eventually. Not the instant bite of the ST3, so an improvement but not as much as I'd hoped. As a side note, when i took the old calipers and master cylinder off i found that the larger 5/8 master cylinder was already on the bike so the improvement is down to having calipers that actually work. If anybody is in need of a 5/8 master cylinder for a sprint let me know. It has all the brake lines and calipers attached but bear in mind both calipers are knackered and would need a full rebuild with pistons and seals.
I think the problem was that the pinch bolts had been done up extremely tightly for a very long time and taking them out made no difference to the circumference of the axle hole. The shoulder on the axle wouldnt go in at all so getting it far enough in to line up with the other fork was a non-starter. I was loathe to put anything into the split at the bottom of the fork to prise it open more for fear of giving myself a catastrophe.