Thanks again.
Ok, the Plaza Prem lounge doesn't sound very attractive, and I had somehow forgotten completely about alternative OW facilities available to me when departing in J with a member carrier, so a useful reminder ^. Was focussing on the default RJ lounge at HKG (as per their own website), but will definitely take your advice and head for one of the preferable CX/QF options.
As an aside, there are (as you probably know) some very respectable lounges within the Priority Pass 'network'. A good recent experience was (surprisingly !) a newly-opened PP lounge at one of the LHR terminals ; have also used some very decent ones down in South America when travelling on low-cost Y-only carriers.
You have a PM.