Historically moving to HE (Home Establishment) was only done to experienced pilots who might be suffering from 'burn out'. Lots of them didn't like it because they ended up as instructors in an era when instructing was a matter of trial and error - mostly error. RAF_lou managed to get to HD somehow. Maybe he could tell how he did it?

McCudden had been on HE and was killed in a crash on his return, so it did happen to some. Often squadrons were formed in England before they went to France. Barker was about to take command of a Snipe squadron when he had his famous combat. And some whole squadrons were transfered there in 1917 when the Zeppelin/Gotha scare was on. Soooo... get onto a squadron that is historically transferred back for Home Defence at that time. 43? 56? One would have to look it up.

Also the RNAS was responsible for the coastal defence of England at that time - mainly with flying boats. I don't think there was any posting from the RNAS to the RFC and v.v. until they were both merged into the RAF.