Buttline, not sure about shipping from the US but i recently bought an 'N' reg into the UK from Europe. Initially it seemed complicated but turned out to be straightforward in the end. You might need to consult an aviation Lawyer to get all your facts in order which although costly is less costly than sorting out tax issues at the port of entry!
As to using a 'N' reg here in the UK for commercial gain, hire & reward etc, very difficult. The CAA are not keen that foreign registered a/c take a living away from UK registered a/c. Having said that it's not impossible but a dry lease contract is usually the way. A potential client would dry lease the a/c at its DOC, hire the pilot separately and then pay the incidental costs, fuel, ldg fees etc.
The other fact is that its unlikely that a company would take your a/c on its AOC unless they sold it to you in the first place, i may be wrong and stand by to be corrected.
If you are intending to bring one in make sure you understand the rules within th ANO for public transport, floats etc for singles, if its a twin then not so much of a problem.
i've probabaly only scratched the surface here and there are many more knowledgeable dudes around with this sort of information, but i hope this helps.
Personally, i would stay in the states and enjoy the sunshine!!!