The easiest fix is to replace the whole mechanism, it's a lot less fiddly than replacing just the cable. There is no EASY fix. You'll have to check the motor as the gears are just plastic and the loose cable being spooled into the gear housing can strip them. In any case, all fixes involve removing the entire mechanism.
Crikey, that cable is hellish brown! I've had three out of five of mine go but they've never looked as rusty as that.
Your options are,
1) get a cable kit for less than a tenner, but a little bit fiddly to do.
2) get a regulator and swap your existing motor onto it (my preferred choice) for about £25
3) get a regulator and motor complete for a considerable amount more. This is the easiest option but if you're capable of taking the regulator out, you should be able to cope with the top two options I should think.
No point in bothering with second hand components that can wear out. I expect the motor is ok. See if the lights dip slightly when you try to operate the window. If the lights dip, then it's drawing current, as so is likely ok. Only try the switch in short bursts, or you'll fry the motor.What’s the best way to test that the motor is all ok?
If it’s fine I’ll order up a new regulator.
If not...
I can get a genuine, second hand regulator and motor for £31
Worth looking at second hand or best to stick to new aftermarket parts?
Thanks folks.