I was travelling along the M62, westwards as it happens and in pouring rain even on the Yorkshire side, and I switched on my rear wiper. it worked fine but wouldn't turn off. after a while I noticed it had stopped, so I turned it on again and the same thing happened. after about the fourth time it eventually stopped, pointing skywards and now won't work at all. I thought relay but can't find any info on the web or any mention of the circuit. Any ideas?

No relays in the circuit.

Would need to know when in 2010 it was built to show you the right circuit, but I don't think things changed a lot. I'll message you to start a conversation within which you could share your VIN. That would allow me to find the car's build date and so which circuit is most appropriate.

Basically there's an ignition switched 12V and an earth to two of the four connections to the rear wiper. Then there's a pair of inputs that control what it does, wash/wipe or continuous intermittent wiping. These inputs also control the screen washer pump motor, so it would be diagnostically useful to know whether front and rear screen washing are working as expected, or not.

The circuit board within the rear wiper motor can show a variety of faults, from burnt out components to cracked solder joints.