Taken to the dealer on Friday and their diagnostics confirmed the forum's conclusion. New brake pressure sensor fitted under used car warranty.
When pushed the service advisor grudgingly admitted that they had changed two that week but it seems the party line is, "We don't know what you mean". This being the case have emailed Audi UK (Thanks to Peter above for details) to voice concerns that all Audi owners should be getting this part checked and replaced by Audi free of charge. Many thanks to all the contributing members for their shared info and advice 👍
