Guisborough is the other side of Teesside, right on the edge of the north yorkshire moors, right next to Roseberry Topping if you know where that is.
Guisborough Woods was in one of the mags (I think MBR) last month. Its a decent place to ride, steep ups & downs, lots of variety, some good single track through the woods but it would be difficult to find, its hard even in daylight!! Theres also marske woods, and a few other locations all very close together.
Carlton in clevelend and osmotherly are very close to Yarm, they both have a decent bit of riding as well.