Most of the stuff on there is small and under 20kg. You can get it from East Asia into the UK via EMS within 4-5 days. On the other hand, you'll be potentially hit with VAT, customs and processing charges on arrival - but I'll bet, if your order is under £100 or so, ParcelForce (who process EMS) just ignore it for customs purposes. There are potential delays once they're in the UK IF customs decide to detain it for customs processing, since C&E are useless.
The Chinese government heavily subsidises EMS shipping, so you can get tat from China to the UK cheaper than you can get toilet roll from Birmingham to London.
So it's not a level playing field in any case. But if something goes wrong, then you might have an issue.