It sounds like a common Honda fault to me.
Mine was sorted by ripping the cooling system apart, flushing it through and then refilling it.
Also, I found that the Air intakes were blocked by all sorts of cr*p which was preventing cool air getting into the airbox which was also a major cause for my problem so it may even be worth ripping that out and replacing your filter with a cotton one [smiley=thumbsup.gif]
I may be completely wrong because I have no understanding of the workings of bikes or anything else for that matter but I've managed to prevent a huge bill for replacement parts so it may be worth while giving it a go or even looking through a Haynes Manual the next time you're in Halfords
