Is there a hike that will take me through a large part of the United Kingdom?

So I am going to go on a trip through Europe with my best friend next summer. I was wondering if there was some kind of trail that took you through part of the UK. Like around a 100 miles or more would be nice. I was thinking of a sort of backcountry hiking that connected at least two national parks and showed me a bit more rugud yet beautiful side of the UK. Sort of like the Lewis and Clark trail, the John Muir trail, the Pacific Coast trail, etc.If possible I'd like it to go through Scotland because I hear Scotland is simply lovely. It'd be nice if it went through England also, or Wales or really whatever you can suggest would be wonderful! Thank you.