Lidl also have a range of various vegan options including pizza (surprisingly good), lasagne, and burgers.

Quorn has been ubiquitous in stores for decades now. I've never been a fan, but it will do at a push.

The problem elsewhere is insane pricing. I've had a lot of "I'm not paying that!" experiences looking at the veg/vegan options in supermarkets. The prices are completely out of reach for most shoppers.

If there's been a "flop", that will have been a big factor.