> Exceptions are B2B contracts (but they still often have one of those) and some piece work contracts.

In the UK big corporations got a loophole where they can get employees without affording them any rights. It's called IR35 that Tory government amended to facilitate this, as Brexit benefit (the regulation would have been illegal otherwise if we were still in the EU).

It's totally legal to fire employee without any notice for any reason or even pay them below minimum wage.