Being the lazy prick that I am, I only really set about fixing it today!
I unbolted the motor thing from the door and pulled to the side to inspect, and also tried powering it while feeling with my hand what was going on. When powering the window down, it all operates as you'd expect - thing turns, cable moves.
When powering up, the motor makes a noise. The cable doesn't move, and the black thing that the cable somewhat wraps around doesn't turn.
I can't figure out how to get the bloody thing out of the door! Where the cable goes onto the motor thing, there's little white plastic ends on it, they don't seem to unclip. Advice somebody, please!!!
I'm sure DRUSS would appreciate advice too!