I am travelling British airways all the way from Sao Paulo to Vienna (Austria) with a transit at Heathrow. I need to change from Terminal 5 to Terminal 3. Is a two and a half hour transit time enough? In case there is a delay through no fault of my own and I miss the connection would BA put me on the next available flight to Vienna at no extra cost? As an infrequent traveller I am anxious about the transit time and unfortunately flights from Heathrow to Vienna with more hours of transit were all full. So had no choice but to purchase this connection. I would welcome any comments or views re. this matter. Thank you.