well its clear to me that you WANT this bike. so get your ass down to bristol and have a good look at it and a test ride. if its still the bike of your dreams then buy the sucker.
you could sell your 400 and turn up with cash and try for a deal. at the end of the day i don't think its gonna be jumping out of the showroom too soon.
it is a very bad deal, but if you can live with it and the bikes not an out and out dog go for it.