Note: Land COVER refers to the type of vegetation (or otherwise) covering the landscape (i.e. grassland, woodland, water or built environment). Land USE refers to how the land is used by humans (i.e. commercial, agriculture, industrial, recreational etc.)
Land use and cover are quite different from the site designations listed in the first post; these designations may be split into statutory (for protected habitats or species i.e. SSSI, AONB etc.) and non-statutory types (typically designated by Local Authorities i.e. Areas of High Landscape Value, Registered Parks and Gardens etc.) For more info see here and here.
With reference to your original question, there are a number of datasets available in the UK for both land COVER and land USE, namely:
- Land Cover Map 2007 (source). Note: LCM2000 and LCM1999 are also available but it is not possible to compare land cover change between the two timepoints due to different sampling methods that were used to capture the data (see here, p.4);
- Open Street Map (source). Note: this is an open dataset;
- OS MasterMap (source). Note: Requires some expertise to derive classes.
Principally, your first port of call should be LCM2007 (if you're wanting land COVER data). For Land Use data OS MasterMap or Open Street Map will suffice (the former being costly).