hi, i've seen this problem before, It is a door latch fault and the latch needs to be replaced.
there are a couple of ways to get the door open, firstly, the way land rover recommend (its never worked for me though!), take off the weather strip at the bottom of the window then with a torch and a long scredriver, break off the white plastic tag that is on the latch, this, according to LR tech support will allow the door to be opened, like i said though, this has never worked for me.
My way of doing it (with customer authority!)
break the interior door panel off (cannot be removed with door closed), then carefully without damaging the door, smash the latch to bits till you can open the door, renew the latch.
A word of warning though, door panels are about £300 new from LR and are mostly on back order, also it will take you a good 3 hours to break the latch enough to get the door open.