I was at the Towers in 1974 and flew the JP3/5 during training - so, as you say, Rebecca/Eureka and UHF/DF were our only navaids. But sufficient to fly ML nav and the (occasional) QGH/DME let-down, although we did quite a few in the Link D4.
Whilst waiting for a Valley course, I flew some trips in the JP5A with the absolute luxury of VOR/DME! Radials and range rings from OTR and instant knowledge of position above 8/8 - no more need for "True bearing, true bearing, true bearing" from the aerodrome whose Eureka you were using, or, if it wasn't, getting a second DF line from elsewhere. I used Finningley quite often - for 2 reasons: 1-it was on 354.0, so one click away from 243.0 on each manual ARC52 knob (as we flew with 243.0 selected as SOP, but flew on a stud rather than M); and 2-it gave a decent cross-cut angle with Cranwell. Quite a few of us would be airborne at the same time, plus lots of other Lincs and Yorks aircraft. But even though we didn't have SSR available, somehow we all survived without bumping into each other or the ground.
VOR/DME/ILS in the JP5A was so much better, but then came the Gnat with the students' best friend - offset TACAN! Lord know why they didn't include an offset box in the Hawk though. The Valley Hunters had TACAN as well, but rather more primitive than the excellent Gnat system. But at Brawdy, it was back to Rebecca/Eureka in the Hunter 6A/7, plus ADF in the FGA9 - which no-one used except for the odd bit of listening to music from broadcasting stations. One mate happened to be doing a SNEB sortie at Pembrey listening to 'Ride of the Valkyries' on Radio 3, which he said was very motivating!
After another 14 years of flying with food-powered navigation systems, going back to VDF/UDF and no SSR in the Bulldog was a bit of a culture shock above 8/8 in British West Oxfordshire! Bearings from Benson Approach and Oxford Homer in 1990 when even the Brize Flying Club aircraft were better equipped! But we did at least get VOR/DME/ILS in the Bulldog a year or two later!
However, those early days of Rebecca/Eureka and DF fixing were very useful in teaching us the art of developing a mental air picture, of that I'm sure!