Sure, it costs a fair bit to go out to China to find good suppliers, to have a UK head office and marketing operation, and to make a profit. That's where the difference in price goes. Also Hunt will probably be able to buy those wheels in bulk for £300 or £250 each, not £400.
The main benefit of an operation like Hunt is that they largely prevent you buying a lemon - a really poor quality or dangerous wheel from a seller who doesn't know what they are doing, because they put in the time to find decent manufacturers. I can't believe they individually test every wheel they import and sell on. Their two main core competencies, and the backgrounds of the founders, are procurement and marketing.
It's a good business selling decent wheels at a price that its mostly very satisfied customers are very happy and willing to pay. The only minor flaw is that its success depends, to an extent, on people believing that it is something that it is not.
Not picking on Hunt in paticular, same with PX, Flo, and the guys who are re-painting the HongFu frame.