So once I get the door card off has anyone got any troubleshooting ideas? I imagine it's the motor, it's alwats been slower than the passenger side and recently has been a little on and off about working. Both front windows run off one fuse right?
Also is it an MOT fail to have a driver side window not able to open because of this?
If it was running slow, and now has stopped altogether, chances are that it's now burnt out and will need replacing

You could detach the window from the mech, and try running the mech on its own - if it's still working it should move okay without the weight of the window. I guess there's also a chance that there's a broken wire somewhere, so check that power is getting to the motor.
If the mech is still working, grease up the runner, and ensure that the window moves up and down in a straight line (no tilting/slanting under operation). There are some nuts in there iirc which allow you to adjust the angle at which the window operates on the runner, however it could be that the plastic guides on the runner have worn.