@garywh Apologies. I missed that you have the W222. There is a hybrid battery for W222 from the same seller on Aliexpress but again, not sure if compatible with your car, and it's around £6,800
Might be worth contacting them (and others offering hybrid batteries) and asking to be kept informed when they get a battery in that matches your specs. Your ordeal does sound very frustrating but unless you can get the battery repaired by someone (UK or outside) then it's a case of waiting for a W222 S400h to be written off somewhere in the world and getting first dibs on the battery.
If it was me... £6,800 plus shipping plus customs(?) plus 20% VAT plus fitting plus disposal charge... for a battery of unknown quality and with practically no warranty (if the new battery failed, you'll need to pay shipping back to China, shipping from China, potentially taxes again, and refitting again on top - hardly worth it) - I'd get it repaired in the UK with a good solid warranty instead, parts abd labour, or just leave it as it is and live with it. Personal opinion.
Unless the OP wants to repair it on the cheap then quickly Px it before anything goes wrong again.