Ian, I should have realised that the Rebecca/Eureka system was part of the IFR (later AAR) setup. I know with the 200 Mc/s setup that Rebecca could even be used as an emergency comms system but can't remember how. We only used it on the Varsity.
With our kit you could do a Rebecca homing by balancing the left and right strobes on the CRT and also reading the range. I believe on the Provosts it was improved and there was a left/right needle as well as a range readout.
As a navigation aid Tacan was far superior giving both range and bearing and more accurately too. For air-to-air use Rebecca had the edge as A-A Tacan had no bearing facility.