dmbperformance

Hi,
I have a problem with my 2004 530D, Iv been having trouble with various warning lights showing up on the screen such as ABS Control System Failure, Charging Fault & Run Flat Indecators warning lights ect. Iv had the car in BMW today and its cost me almost ?1000 and the problem is still not fixed. They (BMW) say the problem seems to be caused by a variation of the car over charging and under charging but they have not found the cause yet. ( This Dealership is newly opened and iv been told by some local private mechanics that perhaps this Dealership does not have their tecnitions properly trained up yet, I dunno though... ) I have to take the car back next week but im afraid of another bill for ?1000 or so and the problem not fixed. Im also thinking that they may well know what the problem is but would prefer take another days labour costs of me and replace parts that might not need replaced atall.. Iv had this experience with a Mercedes Dealership some time ago. I would be grateful if there is any experts that can give me some advise as to what the problem maybe ect.