Honey fungus. What a nightmare! It was in my previous garden. A very knowlegable person gave me a list of plants that are more resilient to it, and gave me the advice to disturb the soil as little as possible so I had some success. Here are some plants from th list:
Ash, beech, catalpa, chaenomles, clamatis, cottinus, eleagnus, hawthorn, Kerria, mahonia, pieris, tamarisk, laurel, larch, rhus,
These plants could be affected by it. I also uased to go out armed with disposable gloves and a plastic bag and try to catch the fungus early, then dispose of it -.
Garden organic web site was very helpful as well,
Good luck