hi i am having similar sorts of problems so perhaps i can help you a bit,
you should be able to ring your local dealer and get the eka code from them, just hope that you have not had your becm replaced inbetween time or that could cause you a problem. as for your battery flattening i would hazzard a guesss that just like my poorly car it may be picking up wifi signals etc and not letting the becm sleep, try disconnecting the aeriel from the rf receiver , just means that you have to be really close to the car to unlock or you could replace the rf receiver, but i am sure more knowledgable people will be along soon to fill in the gaps in my knowledge
regards
dave