I've just come across a very useful tool on the National Library of Scotland's website (of all places).
NLS have put a very large number of old maps of England and of more interest to us, of Kent on line. They can be zoomed in far more than the free English websites will permit
What I have found is the ability to overlay the maps with Bing maps and satellite imagery enabling fairly easy comparison of changes over time.
The link should take you to Warden Point.
Near the bottom of the left hand box below where it says "Change transparency of overlay" there is a blue slider button to change the view from old map to new map/Satellite image.http://maps.nls.uk/geo/explore/#zoom=17&lat=51.4166&lon=0.9012&layers=176