The CAA Safety Sense leaflets contain loads of good info about many things, and can be found at:
http://www.caa.co.uk/srg/general_aviation/document.asp
Follow the link for Safety Sense Leaflets, the one with the OHJ is called SSL6 - Aerodrome Sense.
There's also a sort of 3D poster depicting the OHJ under the link GA Safety Posters on the same page.