If it's a 20v/t with the meta alarm it's easy enough to disconnect the alarm, just unplug the light blue connector hanging next to the fuse box. If that doesn't fix it then probably the relay inside dash end panel is at fault.
Central locking won't be affected by disconnecting the alarm as that's handled by the control unit under the drivers seat, you will lose remote locking though.
There's a fix for the relay by re-doing the solder joints at the pins inside, but that's more for when it stops working entirely, not sure it would help with one side being stuck on.