You can buy buildings insurance on its own in many cases and is the minimum insurance you should have if you have a mortgage. If you do not have buildings insurance you may be in breach of your mortgage agreement.
Ask yourself what is the true cost of replacing all your possessions in your home. You could use a video camera to film it all, then try to do an inventory. Once you have a true value you can then fill in your house owner insurance form correctly with the right value.
Buying your buildings insurance through your mortgage broker can be more expensive that looking around for other quotes. Many though are not aware of the premiums they are paying within their mortgage for insurance. Check out what you are paying and then consider a house owner insurance quote to see if it can save you money.