MG TF 115 locking functions....

Hi All

I would appreciate a bit of help on how the 115 locking/imobiliser should work.

I have bought a 2004 tf 115 which i know does not have central locking. I can arm or disarm the alarm/imobiliser with the fob. When i lock the car with the key it arms the alarm. However when i unlock the car with the key it does not disarm the alarm. Surely it should disarm with the key as well?

Any help or advice would be great.

Also if I was to retro fit central locking, what are the chances of the ecu needing programing? Some say it did need programing some say it did not....