Soldato
But once you've paid your insurance company the full amount, if you decide half way through the policy to change company or god forbid write off your car. Getting any money back off them will be a mission. Paying monthly just means you lose your deposit which is usually 2 months.
I've never had to do it, but I don't see why they shouldn't just refund you, although they'll probably make you wait. Bare in mind when you agree to do insurance monthly you are effectively getting a loan from the insurance company.
It also has the advantage that if you were to miss a payment you get a snotty letter from the bank and a fine instead of having your insurance cancelled.
I relise it's not worth the effort for you because the saving would only be about £30. But when your insurance is in four figures and the insurance company are charging 20% the saving will be £200.