Great video! I can see you have some control on her!
I have been looking for some green lanes around London to go for a quick spin.
Googling a bit, I hit this website which seems to list a few byways around Kent and Sussex. Do you know if it is a reliable source?

http://www.southerntrails.co.uk/byways-in-kent.html

Which tyres were you using in the video? I have got Metzeler Tourance which may not be the best to hit this kind of lanes??

Cheers

P.S. Another interesting site: http://bywaymap.com/index.html