Actually, Quorn is made from F. venenatum, which although a funghus, isn't actually mushroom.
Otherwise, there's always tofu or soy! I know that these foods aren't necessarily recommended, but a small amount wouldn't do you any harm (as you're doing with the cheese/sugar).
You still have brown rice, quinoa, soba/udon, nuts, oats, chickpeas, fruit and veg to choose from. Even if you look at a non-meat-eater's diet, it really won't be that different. You'll still be able to make lots of meals as long as they aren't mushroomy. Oh, and you can still have non-white-flour products.