OK one of those rare times where I feel compelled to comment here but why all this talk about an OCU or training flights?
There already is a training squadron and OCU for the P-8 Poseidon and RAF crew have passed through it and are currently deployed with it training aircrew, VP-30 at NAS Jacksonville.
RAF promotes two at VP-30 Seedcorn Exchange | jacksonville.com
Why set up a UK based OCU when post initial training crew can be sent stateside and pass through USN facilities?