Hi Mark,
The easiest way to remove the Fox gearbox is to lift the turret out the way. Not having a crane big enough, we had to do it the hard way. This involves removing everything from the fighting compartment by taking it to bits and passing it out the front hatch. This is a nightmare job, so don't do it unless you have to.
The Fox flywheel tool is similar to the Ferret one, but longer. Marcus Glenn did have them, it would be worth asking him first. If you can't find one there are several Fox owners down your end of the country, perhaps one of them will lend you the correct tool. You need to remove the panel on the floor at the rear of the fighting compartment to reveal the flywheel. If the engine needs moving to line up the plug with the hole you can turn it slowly with a screwdriver on the flywheel.
It's possiible that the fluid level is a bit low, so you need a lot of revs to get it to start moving, but once it's rolling you are not noticing the slipping quite to much. It should pull of quickly in second gear, I can usually beat people off the lights in a Fox! If the flywheel oil level is ok I suggest you pump the gear change pedal 30 times in the gears which are causing you a problem. If you still have no joy, then you need to start removing floor plates under the turret basket to get to the gearbox and remove the top cover for a look.
You'll need to park the vehicle somewhere where you can spin the turret before doing any of this, because you'll probably want to move it backwards and forwards and round and round several times to try and get best access to the bits you need to see, the inside of a Fox is very crampt when you're trying to look at anything under the panels!
Chris