After some fiddly work persueding all the bits of the control valve to come out, cleaning them and reassembling, I was left with this, ready for adjustment.
Adjustment involved setting the movement of the spool valve to withing 0.001" of the number stamped on the valve. This was 0.101". I borrowed this top quality dial gauge from work and set it pretty damn near. To get it consistently within 0.001" was a tall order.
My kid brother was visiting this weekend, and was a great help in bolting it all back together. After we had bled the system we had a brief moment of panic when everything went up but nothing came down. Panic over when we found out that we just needed a little extra weight (it's all single acting cylinders so everything relies on gravity to come back down).
It's now also been put to useful service with the log splitter, there's a couple of leaks to fix, but nothing major.
It's great to have a sevicable tractor and it really feels that all the hard work has paid off. A big thanks to all those who have lent a hand (both physically and in the form of advice), as ever it's been a joint effort. Not quite there though, it's evident it'll need a new clutch some time soon. I'll take tarting up the body work at the same time, but that may be in a little while.