To be fair England is tiny compared to America. If you *really* want to tour, do England first, then Scotland and Ireland. If you like sheep, you can go visit Dans flock too. A day in London to see all the poop down there, just avoid all the murder and crap, then get out asap! Then a day in Manchester, Newcastle, cross into Scotland into Edinburgh. If you are going with a BF, probably go further into Scotland and find a nice B&B in a tiny town. Then over into Ireland, get wasted a lot, back over into Wales, pet some sheep, and back down to London (avoiding as many gangs as possible!)
I'd say a week or maybe two and you will see everything the UK has to offer. And hear enough accents to make your head hurt
. Then you could continue on through the channel tunnel into France, Belgium, Netherlands (get high) and Germany (do it in October! Oktoberfest ftw!) then if you feel like it, Austria and into Italy.
That's basically Europe. Ignoring Denmark, Norway, Sweden and Finland, which are also nice countries.