It depends what he wants, if he feels like a change then reduce the price and see what he gets offered, he doesn't have to sell if he doesn't get a reasonable price. Go for the lower end of prices and I think the mileage won't matter that much.
Its prob a psychological think that once cars go over the magical 100k miles (95k ok, 105K a lot)
I recently sold a 00 car with 114k miles on it, no big problems, well kept/presented car with 14mths nct. I went for the buy & sell price range rather than cbg or carzone as the latter two seemed to have a lot of dealer cars that would be "looking for" higher prices