An update...
Thanks Chris. I couldn't get it to adjust by wiggling it.
So I took it off and went through the reset procedure here:
http://www.golfgtiforum.co.uk/index.php?topic=186841.0It became obvious at that point where the graunchy feeling was coming from - the adjuster itself felt horrible. I reset it anyway and put it back on. Despite a few hundred pumps on the pedal it wouldn't take up the slack so I think the adjuster is shot.
Eurocarparts don't do a manual adjust cable (according to the guy on the phone) and he didn't have the auto one in stock.
VW have discontinued the manual cable (part number 192 721 335G). However, they can get a new auto adjuster in for lunchtime today - £38 + VAT so I will go with that.
Just sitting and waiting for it to arrive now.
EDIT - New cable now fitted and working. Woo hoo! Mobile again