A nice article on Kent Hills https://www.broleur.com/top-10-climbs-in-the-kent-alps/The lanes around the North Downs are fabulous. There is very little through traffic, so not many issues with cars and most locals are expecting cyclists and horse riders so tend to drive slowly. Lots of hills though.
I had actually planned a route for a Friday's Club Ride called Herons and Hills, that takes in some of the best bits local to me, starting and finishing in Rochester. I will definitely be running this as soon as possible, so will let you know. This includes one of the toughest hills in my area; Lockyers Hill. It is relatively short but is at least 25%. In the winter, getting a grip on the fallen leaves can be tricky.
Here is the route
This includes Birling Hill that I climbed on Sunday and of course the aforementioned Lockyers Hill.