I read something about this the other day. Its not just BYD but other Chinese makers, and expected to affect some other Chinese makers planning to enter the UK market soon. Its partly the shortage ,and long delays for parts, but also a lack of information about how the cars can be repaired.
The Uk insurance industry claim its because the Chinese makers dont understand the Uk market, where insurers strive to return damaged cars to as good as new in the shortest possible time (But not necessarily cheaply
)
But in China and other Asian countries its more common for even quite new cars with a lot of crash damage to be repaired in a very labour intensive way by a large workforce of very low paid panel beaters.
Thus the Uk repair/insurers often write off a chinese car thats should be repairable. But they are not squeaky clean. No doubt many are bought cheap and repaired cheaply using more 'traditional skills' ,and making use of used parts etc. . (or stolen parts which again puts up insurance premiums ).