It been to the local wrench, who sorted out the bent derailleur - its better, but is still slipping around in the middle gears.....

It behaves itself in top and bottom (so to speak) - so me thinks that points to:-

1) Take the chain off and soak it / replace it
2) Try and find a replacement rear set - any advice / links much appreciated, as the wrench said "can't get them, John" (but in Swedish)
3) Get silly and replace the whole hub with a more up to date 6 gear setup (but then we are into spending money) and presumably that's going to be fun finding one that doesn't need me to change the wheel / wheels as well...?

Its rideable, just needs some persuasion to settle down and stop slipping between gears - considering my power riding skills (not) - its liveable with.

I had forgotten just how much more complex it is, changing gear with the selectors on the up-tube - gives one a new respect for the olden days.... (wobble, grab for gears, wobble etc <= me) and they did it at speed as well...

I am very grateful for all the help - I wish I could provide some help in return....