USA.....or Spain. meh neither.
I would never leave England. I have visited USA and Spain on a number of occasions and like the countires however, I haven't seen any reason to move to Spain because the obvious language problem and the fact that the country is in massive debt and has no jobs. There is a large (million strong) British group in the South of Spain but even still with my Norther European skin I would sizzle in the 41 degree heat of the summers.
As for USA, most places the climate is too severe for me, I have been to New York, Nevada, California and Florida and the places in which seemed the nicest were way to expensive to live. Also law sucks in America with criminals and gangstas roaming the streets (okay thats not true but crime is higher than the UK) In addition, its a completely different lifestyle to the UK. You can't jsut walk into town and visit hundreds of shops within 10mins of your house. Due to the vastness of the areas you have to drive for 5 miles to reach anywhere. Also education is poor in America compared to England. Well, some areas anyway.