I'm planning a two-week trip to England (my very first!) in May 2018. For ten days, I will be traveling with a friend; for four days, I'll be on my own. Two days at least are already committed to the Royal Windsor Horse Show and Windsor Castle. Along with all the London sights and a visit with a friend in Colchester, I'd like to visit Canterbury, Dover, Hastings (Battle), and possibly Brighton. How much time should I allot for each place? Should I plan to spend a day in each place, stay the night there, and travel on in the morning? Should I rent a car or is the train/bus system good enough there? Besides Battle Abbey, what else is worth visiting around Hastings? I'm toying with the idea of taking a train from London to Canterbury, renting a car, seeing the sights (sites?) along the southern coast and then dropping the car off at Gatwick and flying out of Gatwick or take the train up to Heathrow.
Thoughts, suggestions, recommendations, please. Thanks in advance.