SM5 power windows dead

Sounds like a faulty regulator, but before you go ripping the door apart, have you checked the wiring harness where it passes from the body to the door? Those wires can fatigue and break over time, leading to intermittent or complete failure. Also, any weird noises from the window motor before it died?

Good shout on the wiring harness, will give that a look-see. Didn't notice any odd sounds from the window motor, but admittedly, I wasn't paying super close attention. If the harness checks out, is it likely the whole regulator needs replacing or could it still be just the switch?

If the harness is fine and there were no weird noises, then it very well could be just the switch. However, given the stored error code and the complete failure, my suspicion is still on the regulator itself. The switch is an easy check with a multimeter, but honestly, with that mileage, the regulator is a common failure point. Given the hassle of getting to it, you might be best off having a shop check it out.

Cheers for the advice. After checking the harness and finding nothing amiss, I decided to bite the bullet and take it to a local shop. Turns out the regulator was indeed toast. Cost me 200€ for the repair, parts and labor. Annoying, but at least it's sorted.