I did it last year on my way around the coast.
It all depends on what roads you're happy to cycle on and which ones you want to avoid as to how close to the coast you can stay.
I'm happy on most roads and only try and avoid major trunk roads, so I found it relatively easy to make the route up as I went along.
When you say stick to the coast, do you mean .......
1:- You go down every road that's closest to the coast,even if they are dead ends.
2:- You mostly follow every road closest to the coast so long as they are not dead ends.
3:- You mainly stick to main-ish roads, but will take some minor roads.
1's the hardest, 3's the fastest, I did 2 ......
Expect it to get "very" hilly in Devon and Cornwall if you stick to minor roads ........
I camp the whole time I'm on tour.
But I'm willing to stop somewhere indoors if the weather gets very bad.
What you don't want to do is carry camping gear and only very rarely use it.
In that case, the extra weight is not worth the hassle of carry it.
Luck ...........
