... or further confused!!
I've seen a few YouTube videos for various trails, all near the southern end and mostly of riders getting lost! I'll take the time as best I can to explain what I believe to be the right trails and how to find them.
The best trail (IMHO) in the forest, even marginally more so than The Full Nine Yards, is the Labyrinth. This is at the southern end and the quickest way to reach is is to go to the Surrey Hill crossroads and climb the steep and wide hill up to the Surrey Hill Reservoir. From here, carry straight on with the reservoir on your right and drop down a slight hill and climb a sandy and not too steep one. From here, straight on again down a rocky wide trail and a much steeper up hill (keep to the right, unless you like walking). At the top, you're on a plateau and avoiding the downhill on the left, you'll see a cut-out in the right-side fence to MOD land with a huge radio mast. Ignore these and follow the trail to the left until after 100 yards or so you come to a (usually there) small pile of sand.
From here, there are 3 small trails all leading downwards.
Two together are Left Left and Left Right. You start between a couple of bushes and within a few feet, you turn sharp left on both. After another few yards, you have the choice of either going straight on (Left Left) or turning right (Left Right). Both end up at the same place and have their own characteristics but Left Right has a very nasty switchback a short way down where there's a f'in big groove that has thrown me off a couple of times. I tend to do Left Left, as it ends in the same place.
The Babymaker starts at the same place but one bush further down. This is a great trail with a few nice table-top jumps that can be rolled down nicely as well. This also finishes in the same place as the other two, which is at the bottom.
Whichever one you take, you'll finish at the bottom, deep in single track country where a load of trails all come together. Whilst there is a quick 'escape' route on the left, the Labyrinth starts where there is a pink/red mark on a thin tree.
With this on your left, you'll see a straight-ish first bit, single track and well enclosed by small trees. This trail has twists, short sharp hills, short sharp descents and a final nice drop at the end. From start to finish it's about 200 yards as the crow flies but with the twisting, it will take about 10-12 minutes to do. If you ride in a group and anyone gets slightly dropped, they will sometimes see the others riding the other way with a single line of small trees between them and the front riders - it's well named, as it really is a maze and labyrinth, except you can't really get lost in there!
Left at the end and up a slight hill takes you back towards where you came from.
So, to summarize, the Labyrinth proper starts at the bottom of the combined downhills of Left Left, Left Right and the Babymaker.
Enjoy!!