Bought myself a GPS device from Cotswold last week for £80. Found it invaluable for locating obscure mines and caves. It gives your location to an accuracy of two metres. I checked out the Raws Level, part of the Old Gang Mines between Swaledale and Arkengarthdale yesterday. Managed to home right in on the overgrown adit with my GPS. Wouldn't have a fat cat in hell's chance of finding it just using the OS map, especially as the Grid Reference is only accurate to 100 metres.

You could also just use your smart phone? They take photos too

Smart phone with geocoded photograph.............. or how about your Olympus Tough camera which has a built in GPS and will geocode your photos

OS maps only accurate to 100 metres? That depends on the map and persons ability to use it. I can't abide six figure grid references for things smaller than football fields. The fundemental lack of precision they give accounts for part of the reasdon the aditnow map data is pretty poor (the fact that some people don't seem to know where they are doesn't help).
Back to smartphones...OSGB have an app which coupled with a £20/yr subscription means you can view the 1K25 maps (and others, but most people tend to use those or 1K50)...and record routes, positions etc. If you know you'll be in an area with poor GSM coverage the subscription does allow you to download chunks (and if you buy the paper 1K25 maps they come with a code that allows you to also download them to your phone/pc).


(don't post accurate locations on here though as Ant thinks it spoils the fun)