Favorite scenic areas with older dog

I'm an (amateur) landscape photographer based in London. I'm looking for suggestions for places I can go for short stays (1-2 nights) to take photos. The limitation is I'll be taking my dog with me. He's getting older, but is happy to walk about 2 miles in a day.

So, ideally places that are within about a 3-hours drive of London, dogs are allowed, and you can reach interesting landscapes within a relatively easy walk. If anyone could share their favorites, I'd greatly appreciate it.