Hi All,
Just to update on my issue.
As stated I scanned the issue with my diagnostic tool. This showed 2 faults. 1 - Hydraulic brake booster and 2 - Brake booster pressure sensor.
I tried to clear the faults but it wouldn't clear the Hydraulic brake booster fault.
Took it to AUDI who stated it would require a new ABS module and pressure sensor. Cost £2,700.
I argued my case that car was only 3 1/2 years old, only done 25,000miles and was purchased and serviced by them.
AUDI paid £1,700, as a goodwill contribution, and I paid the remaining £1,000.