To quote the words from an immortal poet Ms Twain... "That don't impress me much".
Great weekend here, so must just be grumpy and gobby.
People on here, myself included, have over the years had 'great advice' from 'leading repairers and workshops' in their region that has turned out to be absolute crap that has cost them £1,000s. You yourself, as MHM has pointed out, have had experience of a dealer you believe to be "spot on" doing exactly the wrong thing - and you're claiming it to be right. Just as you agree with the statement "If the viscose coupling has failed just replace because it will not drive the back wheels if it locks in place addmittedly it will be permanent four wheel drive but this should not break the transfer box".
So you believe a "leading repairer", a "spot on dealer" and a rubbish statement about VCUs - then gob off on here regurgitating spiel you've been told by 'someone'. Sure, you did a lot of right things when you bought your car, but if you believe that makes you gods gift to anything, you are mistaken. In fact, I believe we may have a new contender for arsehole of the week.
Scrub contender, make that favourite.