What a hassle that was, but the blower is back in action. The blower and resistor in my Mk6 are under the wiper mechanism at the very back of the engine compartment. To get to it you have to remove a large plastic protector above the fan housing that just defied removal. OK it had been there for 21 years! After a lot of pulling it came out in one piece.
Undoing the fan housing was easy but getting it out the engine compartment meant removing the battery and lifting many cables out of the way. The fan had seized and the resistor looked shot so decided to replace both with new parts (didn't want to put a second hand blower and resistor in only for either of them to need replacement again). Managed to get both blower and resistor from the famous online store and refitted everything. BUT, the plastic housing completely refused to go back to its original position and is held, albeit fairly securely, by its two screws.
Turning on the blower and finding that it worked should have ended a very satisfying day, but every time I opened a vent, leaves and debris shot all over the front seats and carpet. Still I suppose the repair could have been a lot worse.......