I only have the insurance on my titanium bike in case of a crash, then I add it to another bike when I go on a tour, but take it off when I get home! The agent doesn't care if I do it, the company makes money for a month or two every year. I get mine through Velosurance/Marko, which I don't think is available outside the US? None of my other 7 bikes have insurance other than what the homeowner's insurance has, but the deductible on that is $2,500 so I won't get a dime for my other bikes through homeowners' policy. There is such a thing as being insurance poor, and you just have to take the risk on yourself and forget paying premiums for anything and everything.
So, if you have several bikes, and one of them is expensive, insure it if it will make you sleep better at night, but I wouldn't do that unless the bike was expensive, and I would only insure the one.
If you buy separate insurance, always get the highest deductible option.