So after reproducing the problem two more times and verifying that a quick toggle of the parking brake resolved the issue for the time being I booked an appointment with the SJ dealer again (3rd time for this issue). They had the car for 1.5 days and dismantled and put back together the parking brake (noting that nothing was abnormal) and again replaced the rear brake pads (surprised they did this as they were just replaced a month or so ago).
I don't know what to think yet, it will take weeks of driving before I feel confident that the problem has been resolved.
I can say I'm super happy with the dealer, they provide a loaner each time (I feel like an old person driving Jags though!). And best of all, they are without question servicing my LR4 for an issue (noise) that they have yet to actually hear because it's rare to occur.
We'll see, fingers crossed.