Willow, I almost booked a flight with Tiger as they were cheaper, but then I saw the charge for the baby and thought, "stuff you!" LOL.
Thanks SS I had a read. I think the difference is that my ticket doesn't include any checked baggage. I am not entitled to any space in the hold according to their rules, but can buy a space subject to availability. Hence my surprise at being told I can have space and what's more it'll be free...