There are many posts on the this subject about how to stop the axle hopping.
It seems the Aussie way to go is to get a new set of leafs made up with a rebound leaf added and the front eye half reversed. This coupled with good shocks (Bilstein or konis etc) will eliminate axle tramp.
I don;t think the rear sway bar does much at all. I had one in my old RS and when I took it out it was actually much better.
The Poms all seem to go the anti tramp kits but these seem to be undesireable on the track.
Though if it's a street driven car and you want to eliminate the axle hop then an anti tramp kit makes sense.
Cheers,
Matt