Presumably they handle the duty and VAT with no extra charges over the eBay price?The stuff comes from china. The UK warehouse only processes the paperwork and stores the stuff temporarily. Basically, they're only a shipping agent. Your order goes to China and your contract is with them.
And the 'Uk' seller is probably not Yosepower as none of the business details match. The kit is Yosepower but may not backed by their warranty service, at least not directly.