Hi VC
Well finally had time to read your thread and peruse their website. they are blagging you mate !
First things first, report the problem to the Advertising Standards Agency, they have just become responsible for marketing on websites, take a screen shot and email it to them and get a reference number.
When/if he calls you back in the morning and states he will not match the price just explain that this is the reference for the ASA and under the circumstances you do not want to go any further but have already reported and next step is trading standards (who i am sure will be interested in them) looking at their track record, immediately report an overcharge with your bank/credit card and get them on the case ! If it was your bank account tell them you have fraudulently been overcharged.
Pressure Pressure Pressure will get you your desired outcome.
If you need any advice or pointers just PM me mate and i will give you my number. (I am an online retailer so know how it works)