You’ll be after the Tour de Gorrick. Haven’t got as a route, because it’s in my head mainly and bits of it are extremely malleable – you can find acres of ST in most of these areas and stay as long as you want and then move on.
Get a map out.
Basically, From Farnborough, I’d head along the Amazingstoke canal. At Norris Bridge do some singletrack stuff all over Pyestock eventually ending up at Fleet Pond. From there cross over the M3 and do Minley and Hawley, loads of ST in there too. From there do Yateley common / Cricket Hill, Trilakes, Wildmoor, to the back of Broadmoor.
Then do Crowthorne woods and all that ST. Then do BlueRedBlue of Swinley, before crossing Barossa/Olddean (sshhhh!!! no singletrack there whatsoever) to the TV mast. Head along the Maultway a bit before turning left into Bagshot Heath / back of Lightwater Ctry pk; not much ST there but lots of steep rubbly hills.
Parallel the road along Chobham Ridges to arrive at Porridgepot. Loads of ST here, and the other side of the road by the golf course (Frith Hill) and then over the other side of the Canal at Tunnel Hill. When you’ve had enough, get back on the canal. But you aren’t done yet, unless you are.
Where the canal hits the Blackwater Valley path go south until you reach Badshot Lea. Then there’s about 2 miles of road to Farnham, where you head up castle street to just past the Castle, and there’s a left turn on Old Park Lane, which takes you to the top of Caesers camp. You guessed it, there’s tonnes of ST here. And then some more the other side of Bourley Road too. Until finally, broken and sore you get back on the canal again at Eelmoor, at the end of the Farnborough runway, and limp home again.
By my reckoning there’s around 80 odd miles in that route and that’s without even finding / doing all the ST in each area. Easily less than 10 miles of road, and less than 10 miles of canal / BV path, so by that reckoning must be 50+ miles of singletrack and forest road. And mainly ST.
I’ve never been great with garmins but I reckon if you put a few salient way points in, you can just explore the ST areas (there’s usually tracks to follow) and when you’ve had enough, head broadly to the next waypoint, and so on.