To suggest that people don't bother with alarms might be a good start since nothing seems to happen when they go off. But crime prevention officers insist that alarms are the best deterrent of crime. Owners just need to know how to set them properly: user error is the biggest cause of false alarms.
Step one: do not resort to force, however dire the situation. Tampering with an alarm is malicious damage and the police can prosecute. Complain to the police, no matter what time of day. When a business installs an alarm, it enters an agreement to lodge with the police the names of two keyholders who live no more than 20 minutes away and have adequate transport to get there and turn the alarm off.
The police will contact the keyholders upon complaint. They investigate all 999 calls and are informed by the security firm that installed it when the alarm has been triggered. The security firm cannot stop the alarm without the keyholder being present.
If keyholder information is out of date, this is technically an offence. The police also give businesses only so many "false alarm" chances in a 12-month period, after which they lose their right to police response.
Step two: contact your local environmental services department. A security alarm without a 20-minute cut-out contravenes local authority by-law. You'll be out of luck on a Sunday or bank holiday, but on a working day you can ask the department's pollution control section to go to the premises and sort out the problem. It can switch off the alarm by any means and charge the premise's owners for the inconvenience. It can even fine them.
Step three: contact your MP about strengthening the system of policing noise control. With car alarms, your local council's pollution control section can, under the Control of Pollution Act, break into the car and disable the cacophony. Unless it has somewhere safe to keep the car, it will be reluctant to do this - if the car was subsequently damaged or stolen, the owner could sue. Most local authorities do not have such places.
Step four: ensure the offending shop or car owner knows how you feel about malfunctioning alarms. Do not accept that noise pollution is something we have to learn to live with. We do not.