Absolutely fine. Mine was a 75BHP variant (High Up!). I'm based in Mid Wales and it was fine on hills and NSL roads. Only ventured onto motorways a couple of times on airport runs but had no issues whatsoever.
I bought another member of the Up! Family for my son, Skoda Citigo Sport, it's the 60bhp version - Group 1 insurance and 55-60 mpg.
Great first car, I also like driving it, its very nippy The Up! Is more refined but I don't think you'll find another Sport branded car in Group 1.