You can look at a sellers profile and it normally states based in China.
What i have found is that there are some very large storage units in the UK for Chinese sellers and most items arrive fast.
Buying from China now adds cost as there is a 20 percent VAT to pay when it arrives and a handling fee.
It may be that as you have bought from a UK site run by Chinese, they may pick up that bill.
A petrol tank i bought from India came with a bill to pay about 50 pounds in taxes and that is sent as a separate bill from customs
I have not been caught for tax on items i have bought from China which are normally just small items