If you intend to do eny mods to the aircraft make sure that the mod has an STC this should keep the CAA fees down but remember they charge about £300/hr.
If you intend to keep the aircraft on the "N" register you must pay the VAT and keep the cirtificate in the aircraft for customs inspection also for flights in some europan states you must have a FULL FAA licence a licence based on your UK licence is not recognised but some states.
As for FAA maintenance that should not be a problem talk to ATS at booker 01494 473664 or metair at elstree 0208 207 3702 both companys work FAA aircraft.