There are lots of place names ending in –dene or –dean around Brighton: Westdene, Rottigdean, Saltdean,Woodingdean, Coldean, Holligdean, Ovingdean, Roedean, Varndean, Withdean. Of course I had to find out what this ending means.
This is what the Concise Oxford Dictionary tells us:
Dene n. (also dean) Brit. 1 a narrow wooded valley. 2 a vale (esp. as the ending of place names). [Old English denu, related to DEN]
Wikipedia has great articles about British toponymy, including a list of generic forms in British place names.
For the origin of French place names, Lexilogos is probably your best bet.