Hello fed up with Audi.
The brake. Pressure sensor location and fitment is well documented on YouTube, with idiot proof guide for us less than competent mechanism.
I bought a genuine one off eBay, for £38, and it took me 2-3 minutes to fit it.
open bonnet, bulkhead offside, pull of the rubber moulding, and lift the plastic panel to access the servo. You will then see the brake pressure sensor attached to a tube which lead to the servo.
on the sensor, pull back the white clip and disconnect the electric plug.
Reach in, and either side of the sensor there are two plastic clips which hold it in place, ease these two clips apart, and pull the sensor upwards. You will hear a rush of air as it disconnects from servo.
Replacement is as easy as removal.
Problem solved in 2 minutes for which the stealership wanted £425!,,,,,,
good luck.