You need to get rid of it if possible or it will consume any trees that you might have. There will be others on here with better ideas than I as to how to tackle it - I am a mushroom conserver but even I would not want honey fungus in my garden :-(

Here's the link to the RHS advice page on Honey Fungus. I hope it helps.

http://apps.rhs.org.uk/advicesearch/Profile.aspx?pid=180

If at all possible, dig the affected area. In the soil you will find what looks like black bootlaces - this is the fungus and must be removed

There are several species of honey fungus not all have bootlaces. I have the non aggressive one in one corner of the garden. It helps see off old/dieing trees/shrubs. I have learnt to live with it and plant resistant strains. When I first found it i thought it was the end of the world but in reality it hasnt been a problem. I lost 2 silver birch 55yrs old, a lilac and a laurel.

As spritz says I had it identified by the rhs and have followed their planting advice.

so there is life after hf. :o)