Hi,
London is similar in size to NYC, but very different. It is another country you know.
If you like London, you will probably like New York. Affordability is always the issue here. I lived in Manhattan 7 years but recently moved to Park Slope Brooklyn, and really love it.
I would check out craigslist.com to get a feel for the housing costs in different parts of the city. Its how we found our apartment.
Good luck and feel free to send me a PM. My wife and I are huge fans of London and hope to go back for another visit soon.