In reply to llanberis36:
Peak District Bouldering gives the high, middle, low traverses - F5+, 6A, 6B+ respectively, either direction. That feels harsh until you have the moves wired ... a lot tougher than grit bouldering grades.
If you take the easiest way for the full traverse you're not going to get much more than a 5+/6A tick.
Rubicon is still a great spot for training your fingers and core and improving footwork. It definitely has its fans.