I want to go everywhere sooner or later, but this would be my first trip.
My ultimate dream vacation is to go to the UK and Ireland for 6 - 7 weeks with a good friend. If you're gonna fly all that way, you might as well stay long enough to make it worth it, right?
We'd fly into London and rent a car then spend a few days in Wales seeing all the sites relating to King Arthur and Merlin.
http://www.legendofkingarthur.co.uk/wales-king-arthur.htm
Then we'd give up the car and take a ferry to Dublin, Ireland and meet up with a two week Rick Steves tour.
http://tours.ricksteves.com/tours08/product.cfm/rurl/code/IRE08/
After that we'd take another ferry to Scotland where we'd do a 7-day walking tour from Ft. William to Inverness which takes you past Loch Ness. Of course I'd score a photo of the elusive Nessie. :) Can you tell I'm into mystical legend type stuff?
http://www.scotland-inverness.co.uk/bht-glen.htm
Then we'd rent another car and spend 2 - 3 weeks seeing the rest of Scotland and England including Stonehenge, Cambridge, and Land's End where Craig Ferguson claims they still talk like pirates.
The last few days would be spent in London seeing all the tourist sites including Big Ben, Tower of London, changing of the guard, do a night cruise on the Thames, etc. and maybe hit a couple of their famous flea markets as well as catch a play.
Then we'd catch a plane and pass out from exhaustion the entire flight home.