Exactly the same problem as everyone else on our Audi A4, 66 plate, 40000 miles. Thankfully had only driven it a few miles with the ABS kicking in before finding this thread.
Thanks to the info on this thread we ordered a new sensor from Derby Audi for £76, it was on backorder but arrived within a few days (first tried autodoc.co.uk for a cheaper OEM part, but as others have said it was posted from Germany after about a week, but never arrived and was sent back to sender by the shipment company for some reason after another 10 days!).
Very easy to change it yourself in 5 mins. Seems to have fixed the problem, thanks all.
