As far as I know, 'Fun in the Mud' is the only off-road training available in Perthshire set up with hired bikes.
There are a couple of farmers in the Perthshire area who have set up off road tracks that might let you ride them if you can get access to an off-road bike. Failing that you might try some of the 4x4 tracks designed for off road driving but again you'll need a bike.
There is a place I use in the borders that hire little 150cc dirt bikes and the guy who runs the business also runs bike tours but it'll mean a trip to Selkirk. Mind you the Glendearg Sortie involves a superb ride over rough country and there are excellent facilities for making a weekend of it.
I've posted details about this elsewhere on the forum so you may have to do a little searching.
There used to be an off road facility up in Inverness-Shire also for bikes but I believe that particular facility closed down.
The Lanarkshire Off Road and Quad Club have an excellent track but no hired bikes but then you're getting further west again.
You might also try Knockhill. 'Fun in the Mud' used to operate from there but I don't know if they have another provider now or not.
Might also be worth phoning Drysdale's in Perth - they might know if anyone runs anything locally.
Failing that you're looking at a trip South of the Border where there is an abundance of off-road schools, greenlane tours, off-road tours and supermoto tours.
I've got several contact details. Feel free to drop me a PM and I'll pass some of them on if you are interested.
