Ordnance Survey maps are arguably Britain's favourite map for the outdoor recreation, but they can cost around £9 for a paper map, or require a paid subscription to access them via the official OS Maps website.
Bing provides access to OS Maps for free across all of Great Britain:
1. Go to maps.bing.com
2. Change the map type (top-right corner) to Ordnance Survey
3. Zoom in
Enjoy the sunny weekend outdoors!
Doesn't work on mobiles (unless you use "request desktop site").
Finally Bing is useful for something!