Is that an official Xiaomi vendor, or just whatever grey import vendors with the "caveats and gotchas", often in Hong Kong or Shenzhen or something.
I did see one online vendor claiming to be "Xiaomi United Kingdom" xiaomi-mi.co.uk...and the site looks very real, convincing and professional,
but the domain is apparently registered to some private individual in Ukraine, contactable by email only. I know Xiaomi definitely has an official retail presence in Russia, and some other Eastern European countries.
When I was in the UK back in February, Out of interest I went to a Carphone Warehouse store, a large UK phone retailer, have a look see what was available. And the only Chinese brand they had in significant numbers was Huawei, there was a couple of ZTEs as well, but that was it.