It has the potential to be relatively low impact if practised sensibly. I reckon that’s about all you can say. 🙂
Personally, the idea of sitting in a car for 7 hours to get a few hours riding in at a trail centre strikes me as completely and utterly insane. There is no way, absolutely no way, I would do it. But hey. 🙂
You asked for a different plan. I’d take the train down from Waterloo to Leatherhead on Friday night, then ride from Leatherhead out to Tanners Hatch YHA on the edge of Ranmore and stay there, either haul supper stuff and a few beers up with me or walk into Westcott for supper. Up good and early Saturday, ride down off the hill in the morning and do a huge Surrey Hills loop finishing up in Dorking. Train back to Waterloo. Travelling time of about 2 hours, tops.