In England and Wales, the vast majority of flats or maisonettes (usually one flat ground and one flat 1st floor) are insured on a “block” or “umbrella” policy. What this means is that the individual flat owners do not (normally) insure their own bricks and mortar.
In the majority of cases their is a single block of flats building insurance policy that covers the whole structure from the foundations to the roof. There are two understandable reasons for this. Firstly, in the event of damage, say to the roof, there is not an argument between which insurer is responsible. And secondly, you can get a better deal by buying one “big” policy.
However, this does not stop it being more difficult to obtain than a standard house, car or business insurance policy. The reason is that it is the type of policy that falls between the personal and business type of product.
You need to make sure that you have a good quality policy with low excesses and wide cover. Most commercial insurance companies will have specialist block of flats building insurance policies, these will cover buildings, loss of rent, property owners liability and glass. As with most financial products, you need to kiss a few frogs until you find a prince (or princess) but getting two or three quotes from different providers should give you enough of a range of quotes to decide what to do.
You will need to gain agreement from the other flat owners, usually best to try and arrange a quick annual meeting where you can all get together to decide what is best.