"Cheaper" is a bit of a misnomer. There is no 50Hr check as per UK maintenance, but 100Hr and annuals (the two can be combined if they concur).
Trusts - these are the American ownership schemes whereby you register your aircraft via these companies for an annual fee. Details in the back of teh usual Aviation Mags but the two most popular are Southern Aircraft Consultancy in Cornwall and Anglo Aviation in the Channel islands
Licensing - correct, you cannot fly it outside the UK unless you have a US licence. Obtaining one of these though is a simple matter of going to the US (after you've let the FAA now you're coming - PM me for the details if you want to know the full process). Main reason for getting an 'N' reg is a more accesible Instrument rating, valid worldwide in an 'N' reg obviously.