thanks for the replies chaps, OMM looking most likely I guess
The KM has a 100mm space Pugsley fork up front, white inds hub on an unknown (to me) rim, apparently a unicycle rim, the wheel and tyre bought from a friend who tried a fat front end on his IF.
The rear is another white inds singlespeed hub built into a Halo 45mm wide rim, the tyre is a 26 inch x 3inch Dura Leopard, its heavy but fits into the back end of the KM just nicely, about 8mm space either side of the sidewalls and chainstays.
Build is a mix of old and new stuff that was lying around.
As for the ride !, well, I fell and cracked a few ribs last weekend so haven't actually ridden the thing yet so will let you know in a few weeks time.
Its been built mainly for coastal riding as we don't get a lot of predictable snow here in the UK, and of course can revert back to a standard 29er for my son to use when we are out riding normal trails.