UPDATE
I got the car back from the garage after they checked and confirmed that none of the tank pipes were crimped or restricted and couldn’t see anything else amiss.
Having read plenty on Jag and Landrover forums about the issue I decided to start with a new fuel filter as they can get clogged enough to restrict the return flow back to the tank. I’m probably guilty of not changing it recently as I haven’t done many miles but it’s maybe 4+ years old.
Swapped the filter today and initially still had the same RP light immediately on startup plus the slight ‘misfire’ like anomaly. However, after a few restarts this seemed to improve, only going into RP when revved and later only when the throttle was blipped, even stalling a couple of times (but OK with a steady rise in revs).
I rechecked the fuel system pressure at idle, which is now fairly steady around 24800kPa. Prior to the new filter it was higher and varying wildly between 30000-43000kPa. Volume Control Valve is at 25% and Pressure Control Valve 11% at idle, which from what I read on the LR forums is about right.
As things seemed to be improving, I took it out for a road test. 5 miles of A roads, a 70mph 8 mile run along the dual carriageway and then back home. All seems fine, no RP light, smooth idle and no fault code logged.
My theory is that the filter was due for changing and the tank removal may have stirred up just enough detritus to block it to the point of causing a problem. I read on the LR forums that the PCV spring in the HP pump gets overridden by the high pressure in the system but ‘fixes itself’ when the pressure returns to normal so I assume that explains the gradual improvement from same problem to no fault after some time running with the new filter and at lower/normal system pressure.
Happy that it seems fixed for now 🙂