In reply to Tom P:
The route you suggest is an excellent way to do it, exactly what I did. Great fun. You do the first morning tootling round a car park and cones on a 125 and convince yourself you will never ride a bike. You then go on the road and by day 2 should be on a 500 cc machine, I had a Kawka ER500 pie eater, great for learning on.
You will spend the rest of the course (3 or 4 days) on this, mainly on the road. Instructor and 2 pupils doing miles and miles, visiting more cafes than you will care to remember and hearing tall stories from instructors.
On the last day you will do a pre-booked test and should piss it. If you don't you should get a retest at the schools expense. You can then ride whatever the hell you like.
VN1500 not really my sort of thing, but I would have thought it a bit large and heavy for starters and those cruiser things are not the best handlers. Would be fine plugging up and down the Mway but round town a bit of handful.
You might be better off with something like a modern sports tourer (emphasis on tourer) something like a Honda VFR 800 or Yamaha Thunderace. My first bike was Ducati ST2, lovely 950 but not hugely powerful by modern standards. Thing is about these machines is that they all have very low centre of gravity and neutral handling and are comfortable on a long run because the sitting position is upright and they are well behaved at low speed.
Ohter things that are good all rounders are things like the BMW big trail bike things (shit off road) but do the biz on the road. For real touring something like a Pan European would be good, might be a bit big first off.
YOu could also think about getting a few months experience on something like a VFR 750 which shouldn't bust the bank and will retain value. Then you could go test ride your real shortlist and make a much more informed decision.