Having a fully inclusive policy isn't always cheaper than getting separate cover. It may be beneficial to get quotes for separate policies as well, especially if you're a high risk for one type of cover.
Contents are defined by the insurance companies as the things you would pack if you were moving home.
Make a complete list of everything including what's in the garage, loft and shed. Photos of each room may help and be a handy thing to have as proof of your belongings.