From OS OpenData developer wiki
Welcome to the OS OpenData™ Wiki.
If you are looking for OpenSpace API and OpenSpace Pro support information, tutorials, FAQs and documentation, please check our new Ordnance Survey web services site.
If you're looking for OS On Demand WMS or WMTS FAQs visit the On Demand pages on our Web Services web site.
OpenSpace API and OS On Demand WMTS code examples can still be found here.