About the only place you can drive it off-road is Balhu (near Truro)
Jim (woodwizzard) and I went there a couple of times with the Toyota Surfs when they had their annual meets there. I can guarantee it wont be shiney afterwards and there may well be a few scratches and dents.
There are some lanes down West (Lands End/St Ives area) but I've not driven them.
Look in
viewtopic.php?f=30&t=16840&start=40#p225003 for our last outing there
Its £10 per day per truck, its only open weekends (not every weekend) and you can drive wherever you wish... at your own risk, as its totally unregulated...and you need to be aware of mortorcycles zooming around. I dont advise you go alone, because you may well need rescuing at some point...I know we did
And welcome