Pressure sender interference triggered 248 times, and steering angle sensor once.
I'm guessing there's a pressure issue! The steering one cleared.
Having read loads on the subject I did some more checks (what a sod it is to get to) and it does seem to be a sender fault:
The voltage varied about 0.2V between brake off and hard on, and INPA showed these:
Firstly brakes off:

Then brakes on as hard as I could:

Assuming I'm reading it correctly, the pressure barely rises.
Anyone confirm or contradict this diagnosis?
**subject changed to try and get some responses!**