Alarm woes

[Alluminio]

Two nights ago (why do alarms always give grief in the early hours...) the alarm on my 2001 A8 4.2 FL began to act-up.

The car was locked in the usual manner and some time later the alarm began emitting, continuously, three loud beeps, followed by a pause, then three loud beeps. The volume of the beeps was the same as when the alarm is triggered, but it was not accompanied by flashing indicators.

All windows, doors and the boot lid we securely shut.

I left the car unlocked as this was the only means to silence it.

Yesterday, the car appeared to be OK, until 1:30 AM this morning when the repetitive alarm beeps began again... so the car was once more left unlocked.

Having searched the forum, I had assumed the problem would be the back-up batteries in the alarm horn, but on reading the numerous posts on the subject, it was my understanding only three beeps were heard when the car was unlocked or started, as a signal the alarm batteries were on the way out. Not a continuous three-beeping with the car locked.

It might be coincidental, but button 1 on the driver's seat memory is now inoperative...

Is the alarm beeping I have described the back-up batteries? If so, would someone point me to a thread which shows the location of the unit with batteries.

The part number of the replacement unit would would be very useful too, just in case time constraints mean I can't embark on a Dremmeling adventure!

TIA

Mark