P3N - How did/is this going? I think legal action is fair, the fault has clearly been a manufacturer fault that's been there from the beginning - hence the many affected users on this site alone. However, the trouble will be you will need an engineer's report to confirm that as evidence in court. I was thinking of doing the same, they might not bother to send anyone to defend a small county court claim.
FADEC - I haven't noticed any difference in braking and have had no issues or complaints. I did some emergency brake tests after changing the sensor and again no issues, very responsive and no locking.
123456789987654321 - The error comes about once your car registers the fault 20 times. Once that happens it bricks the ABS which apparently then cant be reset without replacing the entire unit (£3,000 by the looks of it) or by having it removed by a garage and sent to be reset by a 3rd party (between £400 - £600 from what Ive seen). IF you still have the brake servo message, you should be fine and just need a new sensor. If its changed to a brake fault message your ABS is gone.