If anyone is perusing UK maps, particularly 1840 (upwards) I have put an OSGR / LatLong converter with several map/web links targeted to the location entered. The premise was to make it fast and not rely on the internet for calculation or embedded things.

osgr.mister.red (though if you put it on Fakebook use osgr.mister.red/osgr.htm because Fakebook cleverness doesn't like other's cleverness).

Best of luck. (thinks - I just thought of another useful link to add)