Welcome to AR15.com! You might want to talk to vito113. He's our most prolific Englishman, and he apparently has one of those straight-pull 223 ARs.
And yes, New York City is one of the most restrictive places in the US, as far as gun laws are concerned. But, there are dozens of states that have virtually no state-level gun laws. Most of the South and Midwest have very few restrictions, but the West Coast and the Northeast are generally the most restrictive. Florida, Georgia, Texas, Virginia, and Arizona come to mind as the best, but there are many others. Stay away from New York, Massachusetts, Maryland, Washington DC, New Jersey, and California, though. I believe Miami is one of the few really big cities with almost no gun laws. It's quite liberal, but the rest of Florida passed a pre-emption laws preventing them from making any gun laws.
If you ever come over to the US, let us know (try the hometown forums for the area), and we may be able to set up some shooting.
Just as a warning, there's a lot of political
flamingdiscussion here, but make sure you have a thick skin before you jump into the fray.