D5 (2005 on) D5 Limp woes!

[Oak]

Afternoon everyone - I wonder if anyone might be able to offer any advice?

I have a 2008 MY (57 UK Reg) P3 D5 185 E4 Auto V70.

Last month it cut out on the way back from France. Recovery got it going again but it was in limp mode and has been ever since.

There's one recurring error in VIDA - ECM-P019300 - Fuel Pressure Rail Sensor High.

What I have discovered and tried so far...

New Fuel Rail Pressure sensor (Genuine Bosch) - no change.
Found a small fray on the cable supplying sensor and repaired - no change
Replaced the fuel pressure valve (second hand part but assured working) - made an awful racket - swapped back.
New connection plug on fuel pressure sensor - no change.
Measured voltages with sensor connected and disconnected - all three pins appear to be 4.93V - Even on the pin that "should" be ground?!

If I disconnect the sensor completely I get the same result - the engine is STILL in limp mode and same error (P019300) in VIDA.

I've beared back the loom/conduit and can't see any other wiring issues but haven't peeled the whole thing back.

Has anyone got any ideas what to try next? I've now been off the road for over a month and being an old car I'm anxious not to throw parts/money at it without a definitive plan.

Engine sounds fine, and rev's easily, but I'll not exceed 30mph up hill if I'm lucky. Load off downhill I can get up to 60 ish but as soon as any slight incline - screwed again!

Any advice and thoughts I'd appreciate