I can tell you one thing - jet leg gets worse as you age. Coming back home to Australia is the pits! I'm not sure if it's the direction or that fact that I'm so excited when I'm going I don't succumb to it. There's 10 hours difference between London and here so the theory is it'll take you one day for every two hours of time difference, so that's 5 days feeling sleeping in the day and staying awake half the night. I can tell you how I avoided it last trip - I flew business class!