Got the an issue with keys in my 1999 Discovery II TDI

1. One Key has lost its buttons so it won't open the doors
2. One key (which I bought new last year) has stopped working

STEP 1
With number 1 key I open the door with the key and the alarm goes off
Put the key in the ignition and the immobiliser light goes out and car starts.

STEP 2
Changed the battery in number 2 key,
Tried to open doors with buttons nothing
Tried to open the door with key alarm goes off.
Put key in ignition alarm continues and immobiliser light stays on
Put number 1 key in ignition, alarm stops, immobiliser stays on

Only way to get out of this one is to disconnect the battery then back to step 1.

If I stop the car for any period of time I'm back to step 1

HELPPP!