No, pumping never made any improvement, it was all down to the twin nuts on the shaft of the master cylinder piston. Somehow the locknut had come loose and they'd both made their way up the shaft towards the MS, leaving about a quarter inch of play between them and the lever knuckle they bear up against. However, carrying out what should have been a quick and simple adjustment to take up the play again was anything but as I found it impossible to get two open-ended spanners into the box with enough wiggle room to turn a single flat. A little bit more space would have made all the difference. I had to grind down both sides of one of the spanners in order to complete the job.
