Thanks for the prompt advice guys I'm opting for a modest size back pack ( " Europak ", bought last time in Philippines because my original one was falling apart, inexpensive - can't remember exact cost, 50 X 40 X 25 cm ), and a decent sized check-in case ( " Tripp ", £ 50 from Debenhams, 75 X 50 X 35 cm, 5 kilograms empty ). The case does have a zip - guess the consensus is not to use the padlock, and put valuables, camera, travel documents etc in the back pack.