I too have had the same problem, i went away for a week and when i came back my car battery was flat, so i charged it up and placed it back into the car (Rover 216 coupe 95 model), the thing is when i went to use the remote to unlock the doors and to de-immobolize the the engine nothing happened, i went to unlock the door with the key and the alarm went off, i did an internet search on how to repair it (as you are doing now) and learned that the code from the ECU and the key for was lost and that the only way to get it back ws to have it towed to Rover's and they would reset it all for around £100, well here's the thing, i spoke to a very nice mobile mechanic up the road from me and he said that if i have the battery fully charged (as it wouldnt work with a low battery) put your key into the drivers door and unlock and lock the door 9 times and it works, mind you i opened the drivers side window and aided the locking and unlocking by pulling un and down on the locking button too, great it worked for me :)
John Etherington at roverp5b@hotmail.com
June 2008