BW
FTRS = Full-time Reserve Service
Sounds like a contradiction in terms, but:
You're a member of RAuxAF, work full-time, get paid full-time (virtually the same as regular Rank/TG structure), and get leave entitlement,
AFAIK.
What I'm not so sure about are pension arrangements etc (I was a part-time Reservist, so never looked that deeply into it). Also, not sure about Flying Pay etc. for RAuxAF aircrew (I wasn't).
Well, at least you know what FTRS is now!!