British Airways is useless

We booked flights on British airways for the month of July on a connection flight that would hae landed in London.Also upgraded to Premium Class with extra cost. On the day when we 4 of us arrived to check in we where informed sorry you cannot fly via london as you do not have a visa for london( We were not informed to have a visa as we would only take a flight out in 30min prior to landing there) you must buy tickets on another Airline and there is no guarantee that you will get al your money back. This is unacceptable we made the booking directly on the British Airway website and there where No information to u that we must have a visa. Another couple had the same problem but they where given a solution on the airport to just fill in a form. We were only told sorry you must buy another ticket with another airfare. And the best of all is to get the money back for the tickets the lady cancelled on the airport it a huge struggle. This is useless we where not going into London and are frequent flyers on British Airways as we travel there a lot. But not anymore as of this service.