This airfare is the cheap airfare that I could find because the most fare usually cheap if the passenger buy the ticket from the country that they will departure. For this case if I issue ticket in Thailand for the flight that departure from London the airfare usually expensive more than the ticket that issue in London. So Jon should try to find the ticket from the agent in London if it expensive more than me you can ask me to book the new ticket for him or to pay the fee for change date of his old ticket.