I don't know why you are wasting your money on Insurance, if you fit window locks, then any insurance policy also dictates that you don't just fit these locks but also use them each time you go out even just to pop next door for a minute! They can simply refuse a pay out if it was found that thieves entered through a window that was not secured when you left.
secondly, if you do fit locks, then thieves won't be able to come in, so if they can't come in, then do you really need an insurance, unless they break that window, which is rare as most thieves are opportunist, and will only raid or enter a house that has been left with a window or a door unsecured, rarely they break doors or windows down, as that attracts attention and they risk getting caught red handed, so why do you need an insurance when you have to fit special locks!
In the past 30 years, I have not had any house insurance! and I have saved myself a fortune, let us say at 300 quid a year for 30 years comes to 9 grand, but add the compound interest at say a moderate 5%, you would have well over 20 grand, so if I do get a break in now, i could replace items for all that money I have saved!
insurance is a farce, when you have one, it will make you careless and you would end up claiming! Your premiums go up, so you can never really win in the long term, so why not save your premiums for yourself for a rainy day!