2t Alarm advice E34

[msalts]

Hello. A week ago after taking the battery out of my e34 SE (june '95), there's been problems. At first it was immobilised with the alarm blaring and strange letters appearing on the led screen that usually reads mileage. However, it's much better now since following DueyT's and jofusfarr's very useful exchange here - Here

My car now starts and the led screen seems fine, displaying the mileage as it should.

Problem is, the 2t alarm sounds on doors opening but not until I turn the ignition if fuse 36 'radio' is removed. I've located the brains but haven't changed anything yet.
I've never had a remote key and the alarm hasn't ever done this -
The car is in for its MOT the day after tomorrow so I really need a suggestions/advice.
It's just the alarm, nothing else, no flashing hazzards or indicators etc..
(the 2T siren it has doesn't have a switch)