Hi Jamie
I've live just outside of Tring and have just started laning too, so would also be interested to know of any local lanes. I went out Essex way with the guys from the
http://www.landyzone.co.uk/lz/f13/hertfordshire-lanes-58704-961.html thread at the weekend, and I'm hooked.
I don't have a lot of local knowledge, but the plan is to find any likely spots on the OS map, bung my mountain bike in the back of the landy and go exploring when I get the chance. As carpy said, theres a couple near Chesham and I know of one near Hastoe thats opening on 1st April. Other than that I'm still exploring. I'm going to check out Berkhampstead next week, then there is another likely spot near Princes Risbrough. I'm not even too concerned about finding inaccessible and closed ones as I'll still get a nice day out on my bike
Jason