* "British" isn't a language. It's a collection of accents and dialects spoken within the UK. Some common ones include Received Pronunciation (RP), Cockney, Scouse, and Glaswegian.
* Chinese languages are tonally based. This means that changing the tone of a syllable changes the meaning of the word. English, on the other hand, relies primarily on vowel sounds and stress to convey meaning.
* The pronunciation systems are vastly different. English has a relatively straightforward alphabet-to-sound relationship, while Chinese characters have their own distinct pronunciation rules.
So, while you might be able to imitate some aspects of British pronunciation while speaking Chinese, you wouldn't be able to speak "British" in a Chinese accent in the same way that you can speak English with a Chinese accent.
It's more accurate to say you could speak English with a British accent while also speaking Chinese. You could perhaps adopt some British pronunciation habits while speaking Chinese, but it wouldn't be a true "British" accent.