How long should you wait to fly from london to australia after having ruptured achilles tendon surgery?

Depends: If you are in a cast and the ankle immobilized, flying carries a higher risk of developing a DVT (deep vein thrombosis or blood clot in the leg). If you are walking around than it should be fine. But ideally you should wait until your ankle is not immobilzed.

The concern : Here would be taking a long trip and putting oneself at possible risk for a clot and number 2 being away from your surgeon after a surgery in case you need him. Typically, i won't let my patients leave town after a surgey unless I am comfortable with the way the surgery is healing. The flying issue can be controlled by you moving around and discussing with your doc possibly taking an anticoagulant.