Dr Johns is an excellent trail. I’ve ridden it several times but only recently found there’s an extra bit on the end you can do too. Towards the end you re-enter the woods on the same side of the fire road you exit onto. When you come back out on to the fire road cross over and there’s a short section here. When you reach the fence push your bike uphill and follow the fenceline around to the left. There’s a great bombhole here, then a couple of sloping drop-offs to finish.
I’ve never heard of the Lawnmower trail though. There’s a couple of downhills I do know of opposite Staple Edge Bungalows; ones a straight and screamingly fast one down to the entrance to Mallards Pike carpark, and the other’s a footpath heading north of the bungalows; is that the one you mean psling? If it’s not can you describe the start a bit more – I’d love to find it.