What do you own?
Normally you will own the interior of the property, including the internal surfaces and the walls and ceilings. The external or structural walls and the common parts of the building are normally owned by the landlord who is responsible for their maintenance and repair - but where the cost is recovered from the tenants.
What is a lease?
A contract between the landlord and the buyer (the ‘tenant’). It sets out what each party is bound to do. The tenant has to pay ground rent and contribute to the cost of maintaining and managing the building. The lease will place conditions on the use and occupation of the property. The landlord will be expected to manage and maintain the structure, exterior and common areas of the property, to collect contributions from all tenants and to keep accounts.