Thoughts (I have UK and US independent licences, plus a 61.75, so have been around this a bit myself).
- US standards and syllabi are different to UK (they care a lot more about handling, and a bit less about navigation - also the written exam is much easier, but the oral exam much tougher), and you will need some training and bookwork to get a standalone US licence. I rate highly Rod Machado's online learning material for this. Those you can do at home.
- Pretty certain you'll need an M1 (training) visa. Certainly for my recent CPL/IR in Florida, my existing B1/B2 was inadequate.
- There are a fair number of schools in the US who specialise in sorting the visas out and providing training to foreigners. I know a good one I'd use again in Florida, but many others exist.
- A good working rule is to ask detailed questions by email or phone of the school. If the response is "yea, whatever" or "here is our standard package", I should be concerned about their professionalism. A school that challenges your assumptions, includes "well it'll depend upon how well you fly" and so-on, is probably an honest one to be trusted.
Another option may be to see if any UK instructors or examiners are flying through your locality for the airlines and you could do your renewal with them near home?
G