Recently noticed the readout when I turn off the engine that the rear nearside window is unset. Tried the switch on the panel, no noise of anything trying to open and when I push it to put the window up it says window not set. I presume this means the fuse is ok as there must be power

Window not set mean exactly that! the becm is not set for the windows full height.its lost power at some point
Probably the motor has failed! Theres quite a bit of electrics inside it
when I got my rangie had what sounds like the same problem,I replaced the motor and all is now well
if you do get a new one note that the motors not all the same.
the rear left and front right are the same and the rear right and front left are the same

forget the above. Ive just pulled fuse 12 as the rear window heater was constantly on.
It was draining the battery and just read the fuse layout in rave and seen its for the window as well. Also read the rear demisters relay is in the dreaded box under driver.
It was like a woodpecker before I pulled the fuse to the demisters, so the box of tricks must be faulty

It does sound like the becm has a fault, & if you haven't burnt it out, it could be repaired.
Try putting 12v to the rear window motor & see if it works, which then tells you the becm has a fault.