jul:. Can they significantly reduce/refuse a claim even when there is no mention of it on the policy booklet? Thanks for advice.
Usually if the insurers have applied a discount for having an alarm, they would apply an endorsement. You will need to see the endorsement conditions which will be with the paper documents e.g. schedule and not contained in the policy wording, to see what is says.
Without knowing whether an endorsement was applied and if so what it says, I cannot offer an opinion as to how not setting the alarm would affect your claim.
If there is no endorsement or any endorsement simply states that a discount has been applied on the basis that you have an alarm system that is annually maintained, then not setting it, will not affect the claim.
If there is an endorsement which states that the alarm must be set whenever the house is left unattended, then the claim could be refused.
I would think that if there was a condition that you had to set the alarm each time you left your home unattended, you would know about this. Under FSA rules insurers must draw your attention to any important terms or conditions that apply to your cover. So I think you should be ok, but your insurers will review your policy terms and advise you if there is likely to be a problem. They will appoint a loss adjuster to visit as normal who will report full details of the loss and Insurers will take it from there.
If all is ok with the claim, you should expect that at renewal, the insurers will add a compulsory endorsement, to set the alarm whenever your home is unattended. Then if you suffered another break-in and did not set the alarm, any claim would be refused.
Hope this helps. Don't be tempted to fib to insurers that the alarm was switched on. If insurers become suspicious, this will make matters worse.