One possible way of doing this:
- Download and install Google Earth
- Use the KMZ link from [OSM in Google Earth][1] Earth](http://wiki.openstreetmap.org/wiki/OSM_in_Google_Earth) to display OSM map tiles in it.
- Then use the KMZ from [nearby.org.uk][2] [nearby.org.uk](http://nearby.org.uk/google.html#9) to load OS grid lines in Google Earth, these will show as an overlay on top of the map.
So you can then print out a map from that etc.
[1]: http://wiki.openstreetmap.org/wiki/OSM_in_Google_Earth
[2]: http://nearby.org.uk/google.html#9etc.