Top gear did a test on one of the Bowler wildcats a couple of years ago.
The engine in it is virtually the same as in a TVR griffith.
Especially the sound and accelleration are awesome!
They are however pretty expensive and the mods on these cars are to numerous to list.
There are quite a few contending in the Dakar rally!
See how they build one here: mms://media.rallyraid.co.uk/rally/build.wmv

or go to their website:http://www.bowler-offroad.com/