The EU region has higher tariffs on Chinese cars - the UK has a standard 10% tariff. This is part of the Brexit dividend to UK voters.
No, please don't start the 'blame brexit' debate. Blame failure of consecutive governments by all means though (except politics aren't allowed).
It's not politics or a debate, it's a fact. Brexit has allowed the UK to set it's own tariffs on Chinese vehicle imports, so they're relatively cheap. They wouldn't be as cheap if the tariffs were the same as the EU.