conned at comet

Last Saturday Me and the wife went over to comet canterbury to purchase a american fridge freezer, we saw this american fridge freezer we liked , and decided we would buy it, we was served by two sales assistants , the fridge was advertised for £799.00 with over £350.00 knocked off , we was told the fridge is being reduced due to a store refit, we paid for the fridge and arranged a delivery date , the fridge arrived on the delivery date , the fridge was unpacked and unfortunatly the wrong fridge , we declined to accept it , we went back to comet explained its the wrong fridge, we was told that a mistake as been made at store , and we will have to pay anouther £500.00 for the fridge we asked for , we explained that the fridge was marked up at this price and the sales assistants acknowleged the price , we feel it is unfair for us to pay anouther £500.00 for the fridge we have paided for already , surely there is a contract between the shop and us , and if they have made a mistake they should honour it .
comet have said they would give us a £100.00 good will voucher , but they will not give us the fridge we asked for ,
i have since seen the fridge on the internet for £869.00 and have asked comet to pay for it , if they have my 799.00 plus the £100.00 goodwill they can pay for it , again they refused .
we have not done anything wrong apart from going to comet , so now we are with out a fridge /freezer from tomorrow and cannot get one from anouther supplier untill the 28th October of which means all our frozen food will be ruined , our plan was to receive a fridge tuesday and the next day let the winners of ebay pick up our old fridge , we will honour letting our one go as that was arranged , but we will loose all our frozen food .
Thank you comet for being a nasty company and i hope who ever reads this post will take their custom elsewhere.