According to my calculations, it’s about 12.25 miles on the basis of riding to Hayfield on the road, then up Highgate Lane, over South Head and the Roych then up Rushup and down Chapel Gate. There’s a fair bit on the road, so I figure a couple of hours.
There is a little bit of climbing, but it’s all quite steady. So if you ride back after it’s an extra 24 miles or so, but extendable if that’s not enough. Or less maybe if you go over Jacob’s, though I’ve not mapped that. [about the same that way and back over Middle Moor]
You could always ride over to Chinley and hop on the train there with Sam – Hayfield/Highgate Lane/back road down to Chinley.