http://www.americanexpats.co.uk/

You should also go to the Home Office’s immigration section at http://www.homeoffice.gov.uk/
Follow the links to get immigration information for entering as, for example, a student, an au pair, an artist, a “Highly Skilled” Migrant Worker (many health and mental health-related jobs), etc. (Workers in some fields are welcome, but not others).

There are also businesses that handle/process/advise on these matters. They of course charge a fee, but some of them offer some helpful info on their websites. Just do a good old google search.

Good luck, and you’re welcome to keep me posted!