Colin,
The one area that I didn't do anything with on Darrens lathe, because he had already said he had done something with it, was the leadscrew.
If you can, I would try to get it onto a larger machine and check to see if the end spindles are running true to the thread.
If they are out, there isn't much to play with, but the ends could be turned down and resleeved, then gently turned back to true.
The bearing block at the tailstock end is a real PITA to get adjusted properly, it isn't just a matter of tightening it up.
Remove the tailstock, move the saddle until the leadscrew is just sticking out of the back and use the half nuts to lock the leadscrew in position. Then undo the support block and shim it up and gently tweak it tight until there is no strain on the leadscrew at all.
As already suggested, if you are not screwcutting, the gear train should be set up for the slowest feed possible.
Bogs