N47 520d low fuel pressure

[Dindiesel]

Hi all,
I've a problem;
Bmw 2009, n47, 520d, 260k Miles.
It's throwing 2 codes 4BDC and 4BDA.
To date I have used quality diesel and Mann diesel filters every 25k miles.
So;
Injectors pulled, checked by a guru and 2 swapped out and coded in.
Fuel valve on hpfp replaced for brand new bosch one, no metal fillings present.
In-tank lpfp replaced for brand new bosch one.
Fuel module in trunk/boot swapped for second hand one, no change, fault still present.
Tank filler cap replaced for brand new one.
No evidence of any Fuel leaks at all. All covers removed and pipes scrutinised.
Back probed temp/pressure sensor under hpfp, 4 wire sensor. Ground and signal noted. One signal wire was 3.5v dropped to 2.5 engine running?
Unplugged sensor and low pressure problem still present, no additional code, only that signal lost to sensor.
Fuel rail sensor (front) back probed, signal and ground. I think it dropped to 0.7 volts on engine running but expected as low pressure. Going to swap out for second hand one for cross check.
Rear pressure valve on rail not checked yet, to do.
Fuel filter is warm so heater assumed working.
Car starts easy, even in frosty weather.
Car drives well but low top end power possible due to high reading from dpf due to inability to regen due to fuel pressure issue.
No hiss of air when fuel cap opened on a low tank.
Possibly drives better before car/fuel heats up, not sure.
At low speeds, revs fluctuating and an elastic band driving sensation.
High speed is fine.
My next step is to change the pressure/temp sensor for a second hand one, €40.
I've exhausted YouTube and Google for answers.
Any help would be greatly appreciated.
Thanks