ACTUALLY.............. i kinda see the guys point, if he wants to spend £££ let him, his choice, we can only advise.
I do know that you can run an OFF ROAD vehicle "ON ROAD" but it will NEVER be a true on road vehicle, or seen as such from personal experience.
That said, i have been racing my TT EB4 S2 against a couple of buddies on tarmac, all i did was swap out the wheels for roadies, drop the suspension and fit some shck spring preload spacers to the shocks to keep it more stable. Nothing else was needed except what was supplied with the TT in the first place (with the exception of road tyres and the wheels to mount them on which i already had). Correct me if I'm wrong here, but I'm sure it wouldnt be hard to do the same to other "Off Road" vehicles like buggies or stad trux.