Anything that forms a permanent part of the property is deemed to be a fixture and is therefore included in the sale.
This includes doors (and their keys), windows, built-in cupboards, wall-to-wall carpets and bar/kitchen counters (and the stools that go with them), as well as plants and shrubs in the garden. The seller may not remove them when he leaves, unless it is clearly stipulated in the Agreement that he will do so.
Light fittings are considered fixtures, but a seller may wish to take with him a chandelier that he bought for the house. However, he needs to specify this in the Agreement, exclude it from the sale, and he ought to replace it with another light fitting, though this can be negotiated.