The NLPG is the first, definitive, national address list that provides unique identification of properties across England and Wales and conforms to the British Standard, BS 7666. Local government, and potentially the public and private sectors, can link their information systems to this high-quality source of addresses and accurate geographic location.
Openness: NOT OPEN
Available commercially see:
According to pricing document linked from that page prices (as of 2008-11-02) start at 3k (single terminal, single region) and run up to 148k (whole of UK for 100-500 terminals).
In 2004, the NLPG’s ongoing central management was put out to open competitive tender as part of the wider MSA public procurement is managed by the Local Government Information House (LGIH – a wholly owned company of the Improvement and Development Agency, IDeA). The contracts for NLPG and its related project, the National Street Gazetteer (NSG), were won by Intelligent Addressing.