. . . I don't want to appear rude here - BUT
Using the Ordnace Survey maps and looking at the brown contour lines (proximity to each other, their numbers in metres above sea level) plus the black dots with "spot heights" which are pretty plentiful, with a little bit of experience, will give you your own "local knowledge". I'm not familiar with ViewRanger but most mapping systems will allow you to look at a strip route profile which, while not ideal, does give you a fair indication of the ups and downs - and how big they are.
As always, like beauty, severity of hills is in the eye of the beholder!