Nobody is talking about trillions of pounds, that's ridiculous. Big companies don't "create jobs" or wealth, they consolidate it at the top among themselves. You'd realise that if you understood economics. "They'll all leave if they're forced to pay higher taxes" is also an argument that has been refuted again and again, since they reap so many benefits from being in the UK and London, beyond tax benefits that are already greater in other countries nearby.

Lasting economic and social investment is how you change things. Shit like introducing free, fast broadband, would help businesses and push a huge number of people into work. It's an essential need in this day and age. Competition in many industries, like ISPs, is more costly and delivers worse service. Cutting everything to its bones, privatising it and selling it off to other rich people, does not create well paid jobs or any lasting wealth or investment in UK communities.