Mhhh, I can’t find what the actual import duties are. The closest I found was this article https://www.whatcar.com/news/chinese-car-tariffs-will-not-go-ahead-uk-government-confirms/n27198 that suggest there is none (unlike in the EU, where the rate is 35%).

BYD sell the dolphin for about 10k in China. So they could lower the price a lot more, and the current price reflects more strategy and marketing than production and import duties