MasterMap

Ordnance Survey's OS MasterMap contains more than 450 million uniquely identified geographic features, representing real world information down to individual address and street and building level. The data is validated by over 300 surveyors to published quality standards, so you know you are using nationally consistent information.

[http://www.ordnancesurvey.co.uk/oswebsite/products/osmastermap/ Ordnance Survey] U