There are a whole host of things that can be causing the problem...

Firstly you to make sure that everything that's in the lefthand boot cubby is working properly.... Radio, DSP, Nav, TV and phone if fitted.. All of those units are canbus controlled and are directly connected to the battery.... so if it goes a bit Pete Tong they can still draw power even when the key is out the car.

The next thing is the battery actually going flat, or is it a starter motor problem? If the battery is going flat then lights, locks, etc will be effected, as opposed to not starting when the key is turned.

The immobiliser can cause non starting problems... your car is of the right age for the key to stop talking to the ECU, normally the pick up unit on the ignition lock is at fault.... the give away is the steering lock not disengaging when the key is placed in the ignition.... before you even turn the key you should hear the steering lock go clunk.

As has already been suggested, there could be a problem with the alternator, a good auto electrician should be able to test it.

Also is there anything plugged into the power / lighter sockets.... cos they all stay live when the car is locked... a potential drain....

As with most things Range Rover 1990's on you need a computer, that is of factory origin, to talk to all the systems to see what on earth is going on.... Dealers will have the correct LR computer, but they charge silly money. But there are also a whole raft of Indy's out there too, but they do need to be Land Rover Specialists... there are only a few non factory diagnostic units that will talk to the whole car... Delphi, Allcoms, Snapon are not complete talk to the whole car units.. they are the sort of things that a local garage or the AA would use It has to be a proper dedicated LR unit... Test Book (LR), Gap IID Tool, and I believe that Hawkeye are some of the few that will talk to the whole car and therefore show up any trouble... Yesterday I couldn't spell Engineer... Today I are one!
Inventor of the 'Guide-o-Matic automatic wheel alignment tool'
Former long term L322 owner, Up/Down graded to a Classic Tractor!

Just got back after a week away (in the lake district) and the ff didnt have any problems. When I said previously that the battery was flat, I mean it could give a pancake a run for its money. Not enough to even turn the engine over for more than one or two very slow turns. One other thing - I always turn everything off, but on occasion the blower will start up after the key has been removed. Sometimes just a slight movement of air can be felt at the vents. Is it worth replacing the JGO000021 blower resistor? QUID FACIUM TIBI
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