Quorn isn't slime mould, it's a mycoprotein grown in vats. Sounds horrible, but hey, that's how we make beer. Of course, mycoprotein doesn't sound as nice. Before I fell off the veggie wagon, I found it useful, sometimes I liked a kind of meaty texture in chili and things. Yeah, yeah, proper vegetarians and all that.
For the record, slime moulds are cool. Look 'em up.
I like the veggie sausages partly because I avoid pigs as part of my not-eating-cute-animals policy and partly because they taste nice.