OK, this is where most people would stop, but there are those who like to step things up a bit. For these people, we have the classical, and some not so classical, hiking challenges. The West Highland Way, in 7 days, or why not try it in 5 days! The Welsh 3000-ers! The Scottish 4000-ers! The three peak challenge (all three UK highest peaks in 24 hours)! And many more.
Here below we mention some of the better known hiking challenges. But there are many more, and the ones mentioned can be tweaked further more make them more bareable or more challenging. It's all about how challenging you really want to make it. :)
THIS ADVENTURE: is going to hurt, make you tired, and will really push you. But you will really enjoy it!

An overview of some of the challenges can be found on these websites:
https://www.redbull.com/gb-en/six-best-uk-mountain-challenges
(We hope to extend this list soon)