Can I suggest you register the aircraft with the Ilse of Man (M register), they validate all ICAO licences and by all accounts are a very helpful and reputable aviation authority. One of the advantages is that it wont matter if the pilots have JAA or FAA licences and you dont need to register it with a trust in the States as you do with the 'N' reg. The 'M' register is probably the future for most private and business aircraft in the UK I reckon.
The King Air is a great aircraft and you wont struggle to find experienced crews in the UK to help you fly or manage it.