About Holly Vincent, I have a theory, but of course it's just my opinion, and I have no proof of that :
around late78/early79, you can see pictures showing Mark with a neck lace, like this one :
http://www.gettyimages.fr/detail/photo-d'actualit%C3%A9/mark-knopfler-from-dire-straits-performs-live-on-photo-dactualit%C3%A9/94103657or on the
live at the BBC cover
or in Rockpalast :
he doesn't have it on Chorus TV show on 14th october 78 :
he has it in Hamburg 28th october 78 :
http://www.mk-guitar.com/?s=hamburg&x=0&y=0http://www.mk-guitar.com/wp-content/uploads/2012/08/4404294895_7ff88fd268_o.jpgand he doesn't have it anymore on the final gig in december 79, after they broke up :
I think that this neck lace could be a gift from Holly Vincent, or at least is related with her.
So their relationship could have started between 14 and 28 october 78...
I think that
where do you think you're going was already composed at this time (demo have been recorded during autumn, can't remember which month, I have to check on Oldfield book), so thats' why I guess this song is not about Holly Vincent, although Ed Bicknell explains that Marks sung it like never before in late 79 during US tour when they broke up (Holly told it to Mark on phone juste bfgore going on stage). But the exact date of the gig is unknown.
Maybe it's on a bootleg we all know...