Re: alarm trouble...
What makes you think it is the alarm?
If you've got a multi meter - disconnect the negative lead on the battery, and put the multimeter between the lead and the battery - and watch the current drawn thru.
Ideally you want it to be less than 200mA- that way a 63AH battery should last at least 2 weeks with the alarm set and the car just parked up.
If it's more than 200mA pull fuses out one at a time until you see the current drop - then you'll have found the culprit.
The usual candidates are:
1) Aftermarket radio - doesn't poweroff as there's no IGN sense (at least on a 156 there isn't)
2) Rev counter has failed and a tail light is dimly lit permanently (I've just had this - it's down to the light test circuit in the rev counter)
3) There is no drain and it's the alternator not charging the batt / voltage regulator has failed. (should read 14v thereabouts with engine running)
If it's the alternator / voltage regulator then have a look at having it rebuilt - if either one has failed you'll have to take the alternator off as the regulator is inside.
Hope this helps.