you can thank the UK for hopelessly rolling over on this issue, its very much a one way street post-brexit, as far as ACMI, the majority of these are opportunist contracts to increase capacity, if the alternative was for UK airlines to employ more pilots to fly additional leased aircraft, both of whom would sit idle over the Winter costing them millions, then those UK airlines simply wouldnt put the extra capacity on, it wouldnt be worth it.
Its unfair on UK pilots, but same as it ever was.