Ordnance Survey is Great Britain's national mapping agency.
Ordnance Survey has a variety geospatial datasets available from the website, but only the datatsets listed on the "OpenData" page are available for free download.
For detailed datasets, layers may be divided according to the Great Britain National Grid.
Some useful datasets include:
Meridian 2: A mid-scale representation of Great Britain, primarily consisting of administrative boundaries and transportation infrastructure. Road networks are simplified to reduce processing time. Polygon data include county and district boundaries, woodland regions and lake regions. Linear data include roadways (separate layers for Motorways, A roads, B roads, and Minor roads), Railroads, Rivers, Coastline and Administrative Area. Point data are mostly related to transportation, including road nodes, roundabouts, and station locations. Also included in the dataset is "Gridded Height", which displays topography at using regularly distributed points.
Boundary Line: A 1:10 000 scale boundaries dataset, containing all levels of electoral and administrative boundaries. Layers include: Counties, European Constituencies, Metropolitan Districts, Unitary Authorities, and Electoral Regions. Attribute data are limited to district name and area.
1:250 000 Colour Raster: A raster "roadmap" showing all motorways, A and B roads, all cities and towns, and many villages. Useful as a transportation base map. Data are provided in tiles according to the National Grid. Note that the world files [*.tfw] are provided in a separate directory, and must be placed in the same directory as the *.tif files before importing the data into ArcMap.
Strategi: An excellent overview of Great Britain providing 21 vector layers relating to Roads, Railways, Airports, Trails, Water Features, Settlements, Political and Administrative Boundaries, Land Use (Wood/Forest, Marsh, Islands etc.), and a variety of "Other" features, mostly relating to Historical Sites/Antiquities, Communications, and Tourism. There are also text layers intended to overlay corresponding geospatial layers.
OS Street View: A very detailed street-level raster, useful as a high resolution backdrop. Because of its high resolution, the data are distributed in small tiles (i.e. the data for one National Grid square is made up of almost 400 separate tiles). Note that the world files [*.tfw] are provided in a separate directory, and must be placed in the same directory as the *.tif files before importing the data into ArcMap.
Land-form PANORAMA Contours: A vector representation of topographic contours, provided in AutoCAD DXF format. Data are provided in small tiles (i.e. one National Grid square is made up of 25 group layer tiles). Height data are stored within the attributes of each feature.
