I thought low level navigation was part of the PPL syllabus myself.? Isn't it Exercise 18B - Operation at Minimum level. I always do one navigation detail with my student where we fly at 700ft agl, in the slow safe cruise configuration. If you can do it on a day when the cloudbase is about 1200ft and visibility is less than 10km then even better I say.
Then also there is Exercise 17 - Precautionary Landing with Power. One should also be teaching bad weather circuits, which I usualy do as part of Exercise 17.