electrical problem on 1996 Jaguar XJ6

Started out with dead battery, replaced. Car started but security system, doors, trunk, gas cap locks would not work from fob or interior controls. Next few days car would not turn over like battery was dead charged battery fully still no change. Had towed to garage they replaced BCM car started but security system, doors, etc. still did not function the guy said he could not program the BCM, ok so now when the car is off the lights will come on blinking by them self and kill battery. I need help? Electronics by Lucas the Prince of Darkness

Asked by for the 1996 Jaguar XJ6
seek diag and est from the dealership