What is the least expensive route for doing South England + London in 4 days? (Departing from Paris) [closed]

I live in Paris and I am planning to go next week to London and Southeast England (Canterbury, Dover and perhaps Battle). I intend to go by bus since this is the cheapest option. I've seen that a bus from Paris to Canterbury is costing about 24 Euros.

So I planned the following:

Departing from Paris Thursday late night and arrive at about 6 AM in Canterbury. Doing Canterbury on Friday, and departing to Dover in the late Afternoon. Sleep in Dover. Saturday: Hiking on the cliffs and a tour on the Dover castle. In the late afternoon, depart to London, and sleep in London.

Sunday and Monday: Doing London, historical and more important landmarks, Camden Town, etc.

I have some questions:

1 - Is this route feasible? I don't want this to be a trip where everyone is always tired. It doesn't seem like a terrible idea for me, but I am not an experienced traveller.

2 - Could there it be a cheaper route? (Like going first to London, then do Canterbury, I don't know). Of course that I am working on reducing the costs by any means possible: Going by bus, sleeping in cheap places, etc. My questions on cost is more about the organization of the route itself.

3 - Any other interesting places near the ones we are going that we can see? I wanted to go to Battle for the historical reasons, but I found it to be too far, rendering the trip more tiresome and expensive. I'm open to other ideas.