Once actually at the Cliffs, I walked all the way along them to South Foreland lighthouse (well worth a visit, although I have little in the way of photographic evidence). Then I walked back, and spent a relaxing half hour watching vehicles going on and off the ferries before driving home.
Looking back towards the port
This is how high they are
Ferries with France behind them
South Foreland lighthouse
A gap in the cliffs
Not only could I see France for the whole of my walk, my mobile phone thought I was in France.
Full set starts here.