Owning your own home

Do you own the loft and / or the garden? (ie will you have to just pay the freeholder to change the use of the loft and / or garden, or will you have to pay to buy it off of them? Remember a right to sole use is not the same thing as long leasehold ownership (ie a long lease flat is a long lease flat - the garden may or may not be part of the lease even if you have a right to use it; the fact that you own a top floor flat and no-one can get into the loft without your permission does not necessarily mean you own the loft, or even have the right to store things in it.)

Apologies for knowing next to nothing about freeholding, as I'm from Scotland where it doesn't seem to exist, but if you do have to pay the freeholder for change of use of say a loft or cellar for more space, then how do you negotiate how much you pay for that? Is it simply a case of haggling?

Is the simplest way just to buy the freehold first?