In reply to Ben_Climber:
You could park at Scales, bit of a walk to ascend via Halls Fell, then back down to Scales Tarn, up Sharp Edge then maybe back down via Foule Crag back down to Mousthwaite Combe. Gives a couple of scrambles rather than up one and down one and bit more interesting and longer than a simple 'round'. Probably 10km or so at a guess.
Or you could extend the length a lot by starting at Mungrisdale, up Bannerdale Crags scramble, down to the convergence of paths at Mungrisdale Common, track along to Scales Beck, up Sharp Edge, along to Blencathra, back down Doddick Fell, head along and up Halls Fell then back to Mungrisdale by going to the west of, then north past Bannerdale Crags and back down to Mungrisdale. Probably around 16km+ and 3-4 scrambles of various lengths and (relative!) 'difficulty'.
Post edited at 10:08