There's quite a lot over the Back Woods area. I couldn't tell you exactly where as I haven't been over that way for a while but you can zig zag your way about heading south east until you come back to the road. Last time I was there I saw some north shore style wooden boards/jumps etc.
New Wavendon Heath has a few little trails here and there, nothing major just short little sections. Again, difficult to remember when I'm not there but you can ride from one side to the other in 5 minutes so just spend half an hour zig zagging about and you can't go wrong really.
First pic is correct, yeah. That second pic is, if you look at the map, the south end of a nice little drop below Fullers Earth Lodge. Start heading west up the hill and look for a little trail on the left. The singletrack approaching Fullers Earth Lodge from the north/west is also quite nice.