"Does anybody know if the Royal Navy has a different policy on measurements for pilot, eg...if too big for FJ then you join as a RW pilot"
The issue is due to Tincan ejection, knee to butt length being quite critical as if you bang out you loose legs on the canopy. As a result RN certainly takes those who have otherwise been ruled out by the light blue, as they predominantly stream rotary.
There was a guy who on my course who was to big for the Firefly so they were going to put him in a Tutor to do EFT, he got chopped at grading.