Currently there is an investigation into online marketplace VAT fraud by overseas (99% Chinese) sellers according to the Daily Mail. http://www.dailymail.co.uk/news/article-4291934/Probe-launched-7bn-year-import-tax-dodge.html
This will be discussed at a forthcoming UK Government Public Accounts Committee Meeting (May 3) https://www.nao.org.uk/work-in-progress/vat-evasion-by-overseas-online-retailers/
I have heard on the grapevine from China (their version of Tamebay) that eBay will be removing ALL accounts held by overseas sellers with no VAT number or their VAT number does not match the one on their seller profile (in Chinese):
Looks like eBay are potentially finally solving this issue. Hopefully Amazon not far behind.