My golf is S registered - I think it's a MKIV
The manual shows F42 for the Radio (25A) it says
F42 is in a block of fuses 3 columns wide and 7 rows deep
F42 is in the right hand column and third up from the bottom.
It's been years since I messed with car radios - I rmember some of them having their own in-line fuses hanging off the back of the unit - but technology moves on.
Hope this helps... Good luck...
Peccavi
March 2009