IIRC Gee was finally shut down around 62/63 so the Nav was probably using Decca which was a broadly similar system.
GEE remained the "Rapid Fixing Aid" for basic navigator training until 1970. Decca was not fitted to the 2 Air navigation School (ANS) aircraft at Gaydon until 1969 although it had been in use on the 1 ANS Dominies and the pilot training Varsitys at Stradishall and Oakington for some time. The Varsitys at
1 ANS were fitted with Green Satin doppler (IIRC) but I cannot recall whether they had Decca or not.
The 2 ANS aircraft had GEE Mk3 but GEE Mk2 was still installed in the pilot trainers.
The VOR/DME fit appeared on the 2 ANS aircraft in 1969 and by the time both ANS were relocated at Finningley as 6 Flying Training School (FTS) all the aircraft had this fit. I do not know whether the pilot training aircraft were similarly modified. TACAN was introduced prior to 1972.
It is worth reflecting that in 1968 all the equipment on the Varsitys used for basic navigator training would have been recognisable to a WW2 bomber crew.
YS