I ended up getting my 2 x F seats, but the way it happened was very unusual.
Called QFF on Friday to request award space again. The rep happily lodged the requested but it returned a "load factor exceeded" response - no luck. Loads were F8 A8 according to EF with no P availability showing.
After the call I thought to do a classic award search on the QF website to see if anything was showing on Cathay, as they occasionally open space a couple of weeks prior to departure.
To my surprise, two F seats on QF128 showed up on the date I requested - despite the space not being visible to the rep, award request getting declined, and EF showing P0.
I snapped them up as a new booking, ticketed within 15 minutes and loads on EF were updated to F6 A6. I've since called Qantas and asked them to cancel my existing J booking - I asked them to waive the cancellation fee given the circumstance (would've settled for charging a change fee instead) which they said they'd do.
So the lesson is - don't rely solely on EF for availability. The booking engine has some magic ability to convert A or F inventory into awards so its worth searching (while logged in of course) if you are looking for an award close to departure. I can still see this occurring - for example three (!) F seats available on QF128 for 7 Jan:
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Yet EF shows:
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