British Airways and transit visas for South Africans

I recently booked tickets to fly via the UK to Germany for a family holiday. When applying for the schengen visa for Germany i was informed that we would all need transit visas for the UK, even though we were only in transit and would not pass through customs. I was never alerted to this or warned before i bought the tickets and when i called to esquire British Airways explained they know nothing about visa requirements. So to apply for transit visa's was about 30 pounds per person and because it was too close for departure it was around another 200 pounds per person to have the application expedited. Eventually i had to cancel these ticket and buy new ones with a different airline, and took a bath of R8,000 per ticket. It would be BA to 'warn' South Africans about this before they spend large amounts of money on tickets.