The UK is negotiating from a weak position since it's about to lose a lot in a no-deal brexit. The UK politicians at the same time need to show some kind of post-brexit win. That's pretty much a guaranteed way to get a horrible deal with someone that can be just barely spun to make enough voters not notice how bad it is (ie: like brexit itself).

edit: Although China is plausible, as in China spending 10 years draining the UK of any worth it can before discarding the husk that remains.