Check the wind direction! I set out from Hexham last week planning to do 90 miles back home to Thirsk via Stanhope. After 50 miles battling a ~20mph head wind I knew I wouldn't make it so headed into Darlington and cut it short. I've done a couple of hilly 100s without a problem, but not into a constant headwind.
Take your time and enjoy it - good luck!
Take your time and enjoy it - good luck!