Brits have been complaining about this ever since the treaty was signed. I think generally we're currently more concerned about changes to our health system.
Actually, given the harshness of the penal system in every aspect including their plea-bargaining facet, the US may as well be the PRC compared to the EU. Also, like the PRC, the US has the death penalty.
Separately, there should be a public interest requirement on extraditions, whether by treaty or otherwise, just like there is on all other parts of the UK justice system.
This is a travesty to the individuals involved in this and many other UK-to-US extraditions and yet another embarrassment to the UK.
Plus the USA is hardly the PRC.