new x5 owner with problems .. battery draining..

[micky2guns]

Hi guys iv recently bought an 2004 x5 diesel iv already had few problems which have been fixed , but my lastest problem is that if i dont use the car for 2 days or so the battery will be flat. iv had aa man out and hed checked battery etc, and we found that iv got ampage drain from something once car is locked up. any ideas or is it a case of pulling fuses etc. really given me a headache already this car. if it helps iv already unplugged the engine pre heater because id though that was draining it first but it still went flat. please help thanks.