Thats a handy link ro.
About a year ago i remember reading on the net that there was a app for Android phones using OS Landranger maps,not sure if it is still on the App's store,i never looked into it as i havent got a Android phone.
But you cant beat a good OS Landranger map though.
UPDATE
here is the link for the Android app http://www.pocketgamer.org/os-map