The UAS medicals are taken at OASC Cranwell, transport normally provided by the UAS. Medical standards equal to that of RAF direct entrants, but only part 1 (basic medical, hearing and eye tests) as already mentioned.
If you can get in as a pilot on the UAS it is the better option as the NAV syllabus only gives you one solo flight.
On a lighter note the UAS Nav training counts for nothing, unlike the pilots side which is your EFT, so stake out your place at the bar and laugh at the unfortunates who have to perform (airborne) in the morning.