Hi Meg888, Leasehold means u do not own the land, but the landlord does, however, you do have an interest in the land if you become a leasehold tenant.
Within leasehold tenancies there are both landlord and tenant covenants, where the parties promise to do something/ not to do something to the property, maybe keep up repairs etc. (it may be worth checking out the Landlord and Tenants (covenants) Act 1995 to see this). So if you do not keep up these requirements then you can, by court order be evicted eventually.
Therefore things like building a driveway etc i would imagine have to be cleared by the landlord first.
As regards to selling your home against your will, i presume u mean when the tenancy ends? You will only purchase the leasehold of the property for the time specified by the landlord (or the tenant who may also assign the rest of his lease to you). This time will be defined and can be ended in 3 ways: expiry of time of the lease granted, Termination of the lease, or forfeiture (where the tenant(you) forfeiture due to non payment of rent or not keeping up the covenants specified).
Phew..... iv got that all out, i hope it is of some use and not all gobbledy gook to you!!!!