Posted: 09/11/2013 at 12:02
We have honey fungus in our garden. If your fungus look like the ones in the advice website link you posted (or are even more yellow / orange), AND if they have that telltale fringe around the stem, AND if they are growing in clusters....well, yes, that's probably the culprit.
Don't despair, though. I got frantic when I discovered it in our (new) garden. And yes, it is pretty much incurable; there is a product called Armillotox which you can buy which can help prevent it a bit, but I'm not sure how effective it really is. BUT....first of all, there are different forms of it, and some are more virulent than others; in our garden it is everywhere, but most trees and shrubs are surviving it. Our viburnum really hate it and tend to die (I've reached the conclusion after five years that I need to give up on them) but others seem to soldier on. Take a view on your tree - is it dying quickly and getting ugly? In which case, time to make an end of it (and do the very best you can to dig out the stump and as much dead wood as possible). Otherwise, I'd say just tidy it up and let it go its own way. Maybe treat with Armillotox if you want to feel you are doing something....!
Do you have space to plant a new tree, that can establish itself in time to replace your old one as a focal point in the garden for when the old one eventually dies? The RHS website has some advice on species that are more or less resistant to honey fungus (eg don't even think about viburnum!) - choose one of those, don't plant it too close, and think of it as an opportunity to create something new!
Others on this site will know more than me, but hope this is helpful from someone who's suffered! Good luck with it.