Very helpful advice on the threaded brake rod Dave, will have a close look at mine although it's never been touched from new.
Regarding the torsion pedal return spring, isn't it normal for the coils to be lightly touching each other? (see below). I can see why separating them may give minute reduction in friction but to my mind the coils should support each other for linear operation. The only way such a spring can become "coil bound" is if it is twisted extremely in a tightening radial fashion to the point it binds on the shaft it's mounted on, which is never going to happen in this application. I just keep it well lubricated.
BTW I did clean my pads the other day with the hot water and fairy liquid recommendation. I have to say no noticeable improvement despite exercising pistons and using Ceratec. I do agree with the initial dead feel although green stuff pads improved this situation, but they operate perfectly well once required pedal pressures are accepted. As DaveW suggests pretty normal.