Ok, so I haven't taken it to BMW yet but I've ordered a BMW specific code reader, the C110. I also did some further investigating, I noticed a fuse had blown so I'll be replacing that soon, it wasn't one of the four ABS ones. I've had the car parked for the last 4 days and I've just gone out to start it, it just clicks so I checked the voltage and it reads 11.2 volts... I've stuck my trickle charger on it and I'll retest it tomorrow, I did have the passenger door open the other day for 3 hrs whilst I replaced the door carrier, could that have drained the battery that much?