Thanks Steve, yes pics would be good but the digi cam is out with the wife for her work at present.....
I have two plugs that are a light rusty brown colour, three that are half/brown and half black, while the last one is as black as the ace of spades.
I don't have any white/light brown ones at all.
So, after finding Denso's spark plug site and looking at the pictures they have there, I reckon I have a serious carbon fouling problem, maybe caused by a leaking injector.....