Hello. OP here.
Thank you everyone for your thoughts. I'm so car un-savvy that I don't even have a multimeter so I haven't investigated the drain myself, I only know that when the AA came out that the draw on the battery was considered in the normal range. ie just enough to power the alarm. The alarm, incidentally, I had fitted 10 years ago. This problem has only surfaced in the last 6 months.
Excuse my ignorance, but if there is an intermittent drain on the battery that has gone undetected when the AA have conducted the tests, how would this explain the ruination of the battery after such a short period of time? The battery(s) don't seem to be able to hold a charge after this two week period. BTW the batteries have all been under warranty so I have inly paid for the original one but you can imagine that I was a bit sheepish when taking the fourth one back.
PS on one occasion I made a point of letting the car idle for about an hour, and still the next day there was nothing in the battery so I don't think it can be caused purely through under-use.
So to me the problem seems twofold;
a) there is something draining power from the battery that has gone undetected, and
b) something in the circuitry is damaging the battery.