Horrible and expensive experience

If I could give a zero, I would. We booked flights through Travelstart to go to the Netherlands. Travelstart booked connecting flights, with the transit taking place on Heathrow. At the time of booking, no transit visa's were required. On the day of our flight, we were denied boarding by British Airways, stating that the legislation changed a month after we booked our flights though Travelstart, now requiring transit visas for our family. Travelstart neglected to inform us of this change in legislation. We had to cancel our flights and re-book at an astronomical cost through another airline. Travelstart refuses to take responsibility for this matter and also refuses to refund our ticket costs. They are only prepared to refund +-10% of our ticket costs. Unacceptable. Travelstart failed to inform us of changes. It cannot be expected from the clients to check other countries' legislation on a daily basis, whereas Travelstart has to stay up to date with changes and then relay them to their clients where applicable. We should have been informed of this. We want our tickets refunded.