Hi Paul
BMW insisted that as the brake fluid was touched by the independent garage who did the 45,000 service, then it was not a BMW problem. BMW eventually changed the brake fluid and retested, and NFF. Daughter had to suck up those costs plus the repairs to get her car back.
Update: probably unrelated, but worth noting.
coming back from the Lake District in the rain (June 2025), the O/S rear brake seized. Car was recovered back to Reading.
Independent garage replaced calliper and pads, then ABS system, as they discovered a known fault with these brakes in that the ABS senses when the wipers are working and applies slight brake pressure to clear any potential water from the brakes . . . .