Spaz,
Some RN and RAF F-35 maintainers have already been hands-on with the F-35B for nearly 5 years during the build and developmental test process. They are subject matter experts and will be the experienced core of 17(R) Sqn at Edwards.
Our relationship with the US on F-35, Reaper, P-8 Seedcorn and Airseeker, as well as all the usual exchanges means that a tour or two in the US is a real possibility for many personnel. It makes a lot of sense to keep the experience where it's needed.