One of our club members bought a DRZ SM and stuck trail wheels on it for trailriding. I rode it around our woodland enduro course expecting it to shake me to bits but the suspension didn't seem all that much firmer than my "E".
He had fitted an SM brake rotor to the 21" front so to swap between his 17" super-stickies and road legal MX tyres was an easy job.

Thanks everyone, probably do it in stages on cost grounds. Start with scouts when road tyres nees changing, then get 21" front with proper roadlegal knobblies, finally swap the rear.

Ill probably look to get a new set of brake discs as well to save having to swap them each time as well.

Maybe i should go there instead of wales for some offroad experience ;-)