Here's an idea ...
With the USAF about to vacate Mildenhall, arrange for a joint UK/US squadron of P-8s to be based there, jointly funded by the UK and US. The RAF supplies the base, including all upkeep and maintenance. USN supplies the aircraft (perhaps on a TDY basis) with USN, RAF and RN crew members. UK pays for the fuel. The base is already to US standards with the necessary bowling alley. The squadron commander is USN with a British deputy. The whole thing is declared to SACEUR, so under ultimate US control.
Everyone's a winner and a damned sight cheaper than an outright purchase.