Hi Steve,
Yeah we managed to get round but it was a nightmare. We ended up taking the pennine way out of Dufton, this presented at first a difficult (but doable climb), however the track was only really suitable for climbing on foot - we did most of it with the bikes on our backs or pushing! So the Pennine Way really is unpassable to bikes from Dufton, you're better off doing the Gregs Hut route from Kirkland.
As an aside, when you get to the top the descent, some of which is paved is awesome - though i'm not sure the guys we were with would agree that that the descent was worth the ascent if you catch me.
I'll be looking to do this again, probs from Dufton or Garrigill and using the bridleway up to cross fell past Gregs hut rather than the PW from Dufton. As an aside we met an angry local farmer who wouldn't let us past his tractor - it was awkward and we had to take a costly detour.
For anyone interested the route is http://www.endomondo.com/workouts/16435889 please forgive me leaving the system on when i got back into the car!
Mark.