Did you read any of what that article said? Where is your evidence that Veganic methods don’t work or don’t produce the numbers of vegetables needed?
I have, over the years made it my business to study permaculture, organic production, and other "kinder" methods of vegetable production. I have even experimented on an allotment-sized scale.
And while I don't doubt that the growers using "veganic"metho d are doing it with the best of intentions, (and might be doing OK on a small scale); they will never produce enough edible plant material for an entirely vegan exponentially growing human population.
They say "they" don't kill pests, that nature does it for them. BUT humans are part of nature and have always, always killed and eaten any local, annoying protein-filled pests that have fattened themselves on crops. Veganic farmers are still hypocritically relying on that happening whilst distancing themselves from it.
On a small scale it might be possible to demonstrate in a highly airy-fairy completely un-referrenced article that Veganic farming works, but it isn't working in a vacuum, and it can't possibly work on a large scale.
If you have ANY better, more academic source material for your magical sky foxes who come along and eat the pigeons who have just migrated into the area and eat a whole field of crops over-night I would be extremely interested to read it. But that's all it takes, one migratory swoop of pigeons and your whole annual crop is gone.
In reality, better yields on the scale that we require are going to be grown using hydroponics or similar methods. This will enable us to avoid killing pests, because the growing environment is tightly controlled and not open to the environment, but it is very hostile to natural local wildlife populations as it provides no habitat.
If a balanced vegan diet cannot be grown and harvested entirely in the UK (or even more locally) as the OP admitted, and if it cannot be grown on the scale required without relying on hostile (but technically animal friendly) methods then it isn't a solution at all. It's a religion.