...UPDATE...CHANGE OF REQUIREMENTS...
Well, I now know which bit the regulator is, and how to dismantle and reassemble it blindfold.

Now if we can just make the damn thing spool properly it'd be good.
So, I'm thinking I manually wind one half of the spool, so the effective window position would be either all down, or all up, leaving the other half of the cable loose on the far side. Then plug the unit in, wind the window in the direction of the slack, letting the system slowly eat up the slack, then draw down the tension, hopefully moving the slider in the process. Next update may be written in blood...
Fortunately before that can come to pass my wife and I are off to test drive a Honda Fit "S" (Known as the Jazz outside the US, the "S" comes with 5 speed auto and paddle shift). She wants something that'll cut our monthly repayments and drink less fuel on her hour long commute. The fact she thinks it looks like a small spacecraft has nothing to do withit! Yes, I married a Starwars geek!

Ford Fiesta Mk2, VW Polo, Golf GTi, Lotus Elan, Honda Accord Coupe V6.
Calypso Red Cali #7683 - Bought at 29,000 miles, and sold at 75,000miles.