Basically some would say your insurer may request an alarm to be fitted by a "professional"
But if it's not , and you already got the insurance without it being a condition then you don't have to contact anyone
Insurer may give you a discount but if you forget to set then you won't get jack
And I said , you don't need to contact your insurer if there was no request to do so when you took the insurance out
Of course if you get robbed and become high risk then on renewal they may request it , then diy becomes pointless
But you don't have to contact your insurer for something that isn't requested by them