Smart money's on somewhere that already has FJ operating. I'd put one more into each of Lossie and Con, but that's a wag. North needs close range Red Air and so does the South. Sticking them at Leeming doesn't really help either, especially when you may not be able to rely upon a tanker to extend. For me the support already there at both LOS and CGY makes it a no-brainer, regardless of the T2 and T3 uncommonalities.
Sqn numberplates will be interesting. I'd imagine they'd come from one of the following: 111(F), 43(F), 19(F), 25(F), IX(B), 31 and 12(B).
Great to know there'll be a decent aggressor for the Typhoons and Lightnings of the future though.