I will be flying back from Jamaica on Tuesday, 8 July. My flight is due in around 9 o'clock but I'm told that flight times and arrival is extremely unreliable. I had wanted to book the national express coach to Luton but would I be able to get a refund if it's too late and I miss the bus? Or if I book it too late in the day and I arrive early could I go on an earlier bus? Would it just be best for me to buy the tickets on the Internet on the day or can I pay up on the bus? Is it busy service?