Thanks for all the excellent info! I have read over a few times even if I haven't replied until now.

I went to a store today and the man recommended a pack around 70L+ of which he had none in store. I will be travelling for about 2.5 months, what kind of size do most people use?

He also mentioned that some bags can be locked while others can't be locked. It didn't seem like a big issue to me as I've never had any problems with baggage handlers but is a lock something that bags should have?

I'll be doing lots of things from swimming to clubbing to outdoors trekking so I feel like I need to fit a long into this bag! (Travelling light seems to be a problem!)