I don't understand why you are upset... vendor A has the product for X pounds. You go to vendor B, who normally match prices and charge 2 x X for the same product, but in this case figure they will lose money on the deal and they pass.
THe correct solution: buy the product from vendor A, use it, and grow old and happy.
Your solution: get all up in a huff to the point that vendor B wants to discourage you from coming back. Then go on the internet to trash them.
The fact of the matter is, a 'price matching policy' is not a sacred covenant entered into by a shop - they are not legally bound to match every price - nor are they morally obligated. If they are not making any money on the sale then why would they want to do it - just to steal a sale from a competing store?
And why exactly are you so upset by their decision? Was there some reason you absolutely needed to buy it from their shop? What if instead of simply refusing the guy had said: "We will offer it to you at that price, but please order it from the online retailer as selling for so cheap would hurt our ability to keep the store profitable. Please buy it online." Would you still insist on buying it from them even knowing the online retailers are happy to sell it at the reduced price? I guess what I am getting at is, why do you think you have a right to buy it from them at a price you demand?
And, for the record, I promise that every business that has a price matching policy has a 'common sense override' where the manager or owner can decide the transaction would do more harm than good to the store they can decide not to match prices... perhaps some retailers enjoy losing money on sales knowing they are stealing a sale from a competitor; some larger retailers play 'tricks' and have a slightly different model than a more commonly available one so they can claim the items are not identical and thus deny the price match; some industries may have such large mark-ups over their cost that they can discount things by 80% (like big box furniture stores). If the business had no such ability, then an ill-meaning small vendor could cause serious hardships to larger companies by offering an expensive item for sale at far less than the wholesale cost, then directing any interested people to a larger retailer (claim you don't have their size, for instance) to force them to lose money on some expensive items.