Thatcham alarm and immobilizer

Thanks for taking the time to respond. Much appreciated. I had door switch replaced a couple of years ago as drivers door wouldn't open at all. Fuse from central locking was removed back then and I haven't replaced it. Doors all unlock and open okay without central locking fuse. The Thatcham alarm and immobilizer ECU memory part has to be cleared by disconnecting both battery leads but maybe I should totally clear memory by leaving lights on as well as heard Thatchams hold a little charge still and last sequences in it's memory, whether it was the good part that started the car, or the bad part that immobilized the engine. If I get engine started it likes me to drive over 30 miles and everything resets itself. I recently drove over 30 miles but stopped at shop and left good working key in ignition with engine running in case it didn't start again and used the key it doesn't like to lock the door whilst engine was still running. If I use this second key it doesn't like it and causes these immobilizer issues, running in This usually limp mode until I drive over 30 miles again. The alarm siren fuse or cable and flashing lights fuse was removed by somebody when battery went flat over winter when I didn't drive it for months following a back operation and alarm kept going off intermittently at night. A new battery was put on and this is when alarm immobilizer problems started. Unfortunately they cannot remember what they removed and from where. If I could work this out and get alarm siren and flashing lights working, maybe immobilizer would reset itself and work again as long as I do not use the spare key in any of the doors which messes it up again with only that key.

Also noticed the other day 4 lights come up on dash. When one went out I tried again and it started but didn't when I tried it again next day.