Marshall et.al.
You should suggest to Bentley that they read the original VW  manual: the
late John Muir's 'Compleat Idiots Guide to Volkswagens'. I've been driving
and working on them for 30 years. tho this book is just for air-coolers,
the basic, common sense stuff and the little tricks contained are the best.
My .02,
Cheers
Jess Lopatynski
86 GTI
87 GL
89 Targa