Ordnance Survey provide some of their digital maps at no cost.
- OpenData - these are free to everyone and are useful for large areas.
- PSMA - under the Public Sector Mapping Agreement, most maps are available for free to central and local government (including parish councils) plus the health service. These provide more detail than OpenData.
Additionally, DEFRA, via their Magic website, provides links to a variety of free UK map resources.
While the maps are free, you will also need GIS software to use them. We use, and can highly recommend, the free Open Source software Quantum GIS.