Really surprised to discover that ADT was the most cost effective out of them all. The reason for this is that my installation only cost £299 which includes the Metropolitan Police Registration fee. The system was installed in about 5 hours with the minimum mess. I opted also for a combined smoke/C02 detector that alerts the alarm receiving centre if I have a fire/gas leak. Most quotes I got were around the £900 mark plus the £300 or so a year
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