[memracom]

a) keep working in England. b) blog about the apps that you are working on so that the world recognizes you as an iOS expert c) attend a conference in the USA, preferably somewhere from Chicago eastwards to maximize the number of New Yorkers in attendance d) make it known to everyone that you, the well known English iOS blogger and developer, are looking for a job in New York with a company who will sponsor your visa. e) when somebody bites, be ready to suggest a New York immigration law firm who specializes in helping companies through the process because chances are this will be the employer's first experience with visa rules.

And while you are doing all that, do keep an eye on http://newyork.craigslist.org/sof/ for jobs and write inquiries to see if they would hire you on a visa. Also get a good education on US visa types because H1B are hit and miss. A visa that leads to a green card is a better bet. If you can identify any agencies (ad or design) that have offices in London and New York, ask them if they hire iOS developers and if so, would relocation be possible. Internal transfers in a multinational company are the easiest way to go.