My rear windscreen wiper has a life of its own. It comes on and off intermittently sometimes wiping ever 5 seconds, sometimes 10 minutes, sometimes off for hours. Any suggestions please.

Assuming that intermittent is switched off, the rear windscreen wiper activates when in reverse and also teardrops when the main screenwipers are on (unless you have switched that out).

As above, have you checked the settings on the info unit?

Look on the radio in the car section under wipers. There is a tickbox for auto for the front wipers and another tickbox for the rear wiper, although the rear one doesn't have a rain sensor as far as I know, so presumably has some techno mumblejumble for working out when to wipe from the front sensor and at least in my case, generally gets it wrong.