classic range 300tdi battery drain

hi,
I am new to your fantastic forum, and need help..
I have a '94 soft dash classic range rover 300tdi..
Since owning the rr,if i leave it overnight,i come out in the morning to a flat battery,its not completely flat,but does not have enough power to start it..I have put a couple of batteries in it and the alternator is charging fine..stick jump leads on and it will start no bother..the rangie has electric/heated seats and all the other toys and i am wondering one of these is causing the problem.???.
is there a common fault????
I am sick of either disconnecting the battery every night or jumping it in the morning...
Any ideas greatly appreciated!!?? thanks

if battery is good ,and no obvious light etc left on, disconnect alternator and try next morning

Ok,thanks for quick reply.. will try that and keep you posted...