Map Reading Posters on Grid Refs, Shape of Ground, Distance Measuring, Contours & Compass.
MATT5 Map Reading Workbook
Military Map Reading booklet
Military Map Reading guide and workbook. (Requires OS map Sheet 199: Eastbourne and Hastings).
Ordnance Survey videos on map reading. Military maps use mils, not degrees. 360°=6400₥.
Royal Marines military map reading training videos.