TV deal still a bargain.
I placed an online order for a new TV which was advertised at a knockdown price. I received email confirmation but the following day the company got in touch to say they had made a mistake but they would meet me halfway. I could only get the telly if I paid another PS100. Is this fair? Yes, as you don't have a concluded contract at the cheaper price. The web ad is classed as an invitation to treat and your "purchase" is simply an offer to buy at that price. The firm have not accepted your offer but are offering a discount as a compromise.