My wife's car is due its Insp 1 next Friday. £300 is the quote from our next nearest dealer, but that excludes brake fluid and coolant changes; memory (based on her previous BMW) suggests around £100 for those 2 . And the MOT is due, so that's another £60.
Service costs are high at BWM garages, but I think there is an element of peace of mind, particulary when they sold the car from new.