Central locking & Key fob - can this happen?

Hi, I recentlybrought a new Discovery (Not new - just new to me) it is a D2 td5 and is the 'S' spec model (so no sunroof).
It has an issue with the central locking........

........I have two key fobs, only one with a blade.
With the blade fitted to either fob it will start the car no problem, either fob will lock ALL doors also, BUT, neither fob will UNLOCK any doors, so then I have to open the drivers door via the key and naturally the alarm goes mental and continues to do so until I start the car.

Then I operate the dash mounted switch to UNLOCK all the other doors, but the nearside rear door and the tailgate door do not unlock unless you physically open them using their individual handles.

So I rang my local LR dealer and asked about new keys and explained the problem, he said that the keys where probably ok as they LOCK & Start the car, so he said that he suspectted it maybe a duff central locking accuator as if any of them are not working correctly the fob will not unlock the car.

Is that right ?

Also the key only unlocks the drivers door, not all doors (in case thats realivant).

Thanks in advance as I sure one of you will have the answer.

Cheers
Gary.

Just an update, brought two new keys from ebay (they are near identical copies of the originals) so that at least gives me decent cases.
How I am getting around the alarm going off all the time until it can be sorted is this......

....I lock the passenger front door by pushing the button down on the door, then after exiting the vehicle and shutting the drivers door, open the offside rear door lean in and push the button down on the drivers door which only locks the drivers door, then push the button down on the offside rear door and shut it............Car all locked up (remember the tailgate and nearside rear door does not unlock on the dash button) and to unlock it I simply use the key in the lock but the alarm is not set so no noise.

It is only a short term solution but it'll do until I figure out whats going on.

Cheers
Gary

Sounds like you have a fault in your central locking system, it could be in the drivers door module as this is the 'master' for the system.

D2 central door locking is involved andall doors interface with Body Control Unit (BCU)

The locking system can be interrogated using TestBook or similar for diagnostic information.

I have brought (again from Ebay - but gauranteed 100% working perfectly or money back) second-hand Central locking units for tailgate and NSR door, once I fit these, I am hoping this will solve this particular issue.
I don't have any dianostic equipment unfortunately so can't test stuff.

I'll post result.

cheers Guys