Hello, I am a solicitor with over 15 years experience. I will try to help you with this.
That will depend on the circumstances. Firstly it would need to be proved that it was more likely than not that the infection came from your garden. Then your liability will depend on whether you should have been aware of the the honey fungus in your tree, there would need to be a foreseeable risk of it spreading and the damage to their hedge would need to be reasonably foreseeable.
Are any other gardens near you affected by honey fungus? I think on balance based on what I know from you that your neighbours would find it difficult to pin liability on you.
Hi there, thanks for coming back so quickly and it's helpful to have this.