When i arm it (when it's not playing up) it make the 1 fairly loud beep and the hazards flash once and like wise when i disarm it but twice instead.

When it's acting up and i arm it it makes a quieter beep and it doesn't flash the hazards at all (like wise when disarming) basically acting like the car battery is flat (which it's not because the car starts fine when doing this).

When it acts up, if the alarm gets set off, instead of the normal siren and flashing hazards, it makes the occasional quiet beep (as if the car battery is flat again) and if i try to deactivate the alarm it just carries on.

The only way to shut it off is to unlock the car with the key and turn the ignition on (when i do this the alarm starts sounding off how it's meant to and the hazards start flashing) and deactivate it with the ignition on.

This only happens after i've driven it tho as when it's been parked up for a lomg time, the alarm arms/disarms/activates/deactivates fine.

This is why i find this quite an unsual problem