London is divided into 6 zones. The city centre, what people call "the city", is one square mile and it is zone 1. The school you booked (St. George International) is in zone 1. Heathrow airport is in zone 6. Luton, Stansted and Gatwich are outside London but there is excellent transportation to/from all the airports. If you have booked through us, my colleagues will contact the school to see what airport suits you best. So, feel free to let them know that you need help regarding your flight booking.