By control box does he mean the isv controller? it's behind the center console!
Get your self a beer and read this thread
http://www.golfgtiforum.co.uk/index.php?topic=12817.0This happened to me and i went mad for months untill i was told this couldbe the problem! ?380 + VAT or pay the going rate of about ?15 - ?20 for a second hand one!
I got my from radicoolvw vw breakers yard! give em a ring, arange a price and postage (mine was ?20 all in) and send em a cheque, wllhave a new on in around 2 weeks

Details -
Radicool VW - VW specialist breakers yard
Tel - 01202 823060 - Mob - 07970 460 199
Unit N
Long Meadow Works
Ringwood rd
Three Legged Cross
Wimborne
Dorset
BH21 6RD
Note - need to send cheque only, no card payments.
Fitting is easy, unplug old and plug in new one!
All credit to Gambit on this btw
Good luck