Seriously, one of these things is the best part of 1,500 - 2,000m of ascent, give or take a few hundred depending on what exactly it is that you're doing.
That's going to be difficult. There's no two ways about it. There's no magic solution (other than an electric bike) that will make it not hard. You've got to do the work. It's a ton of climbing. Add to that there are no (or very few) flat or downhill sections, where you can recover but keep your legs moving, makes it even harder. Doing that much climbing - it doesn't matter whether it's up a mountain all in one go or in the UK over a series of smaller climbs - is difficult.. Gaining potential energy is hard.
As that famous philosopher Montgomery Scott put it: "Ye cannae change the laws of physics".
Slightly off topic but on another forum recently there was a discussion where someone said something along the lines that riding 100 miles should not be difficult. Now I speak from fairly extensive experience on this point and I've never ridden a century that was not bloody hard. I've never been anything other than completely knackered at the end. Of course, it's easy to some people. But not to me.
