Back in the days when I was a younger and much fitter man (with knees that worked) and living in my native north of England, I used to do a lot of fell walking in the Lake District, Yorkshire Dales, Peak District and, when I moved up there, Scotland.
So long as you have emergency rations, water, shelter, warm clothing and you know how to use a map and compass (especially in bad weather) you should be fine.
Wild camping is great fun but don't forget that it's not universally legal in the UK and it's always best to ask for permission (and tips on the best places) - especially in National Parks. One issue to become good at, is not leaving a mess. The link is a really worthwhile book that will ensure you are as enviro-friendly as you can possibly be.
My suggestion for camera gear is start small and see how you get on. I used to find lugging a Mamiya C330 was a pain - but if you can manage a 5x4, then why not....?