I have electric folding wing mirrors on my 64 plate C-Max and the driver side isn’t folding in when locked. Would this be a case of dirt in the motor or is the motor totally knackered?

Sometimes you can get lucky by soaking the pivot with penetrationg oil and working the motor in and out with the switch on the door. but you only get a few tries before the relay trips out if done in quick succession.

if you can hear the motor trying to move the mirror when you lock the car then give it a go. if nothing at all, then the motor or wire inside the casing has gone.