Great question Haggis.
I'm pretty lucky as I'm close to some great laning areas. I'm between whats called the Peak District-Derbyshire, as well as Shropshire and North Wales. Only about 15 miles to the closest 'quality' 'Green Lane', which are technically called 'Byways Open to All Traffic' and 'Roads Used as Public Paths'..... BOATS and RUPPS.
On a map these lanes are usually green, hence the name
most are unsurfaced, from easy to gnarly.
These lanes are usually from less than a mile, up to 12 miles. We have to string them together between normal highways, though you can put together enough to do 2 days in quite a small area, around picturesque villages with pubs and cafes.
We often just pack a picnic, go do some scenic lanes and have a day out!
You'd be lucky to get 'lost' and you'll never have a day without bumping into mountain bikers (which I am and what I do for a living, working for a big website) trail bike riders and ramblers.
There is always pressure on getting these lanes closed due to erosion, noise, anti social behaviour etc. Ramblers in the uk have a 'right to roam' and we get scowled at by ramblers on every trip, no matter how polite we are. A lot of gnarly lanes get closed due to 'erosion' though it's mostly erosion+aggressive tyres !
I'd love go to the US to see stuff I see on ExPo.. Even just Tea Kettle Junction, The Racetrack or any of Moab, to name a few.