FWIW, Martin & I mooched round a El Supremo perm yesterday (Buckbarn - Sutton Scotney), riding round well trodden, er, ridden roads in Southern England. Had a bit of everything, sunny skies, gray skies, drizzle and occaisional deluge(s), big rolling hills, wooded climbs and descents and (owing to a late start) a couple of hours on pitch black roads (as we hadn't anticipated being out late we had only brought our commuting lights with us).
So, a standard AUK perm really. Mile for mile, it seemed way harder than PBP.