The answer is that both are correct! Ageing is the form that is more commonly found, although aging is occasionally used. The norm, of course, is to drop the final 'e' when forming the participle: Rage becomes raging as in: 'The storm was raging.

Is there an E in aging?

Aging (spelled without the “E”) is the standard spelling in American English spelling. If you are writing to an American audience, this is the spelling that you will want to use.

Is it ageing or aging in Australia?

For now however, “ageing” remains slightly more favoured. Q: So for an Australian audience, you'd suggest going with “ageing”? A: We would. But “aging” isn't incorrect (Macquarie Dictionary lists both) – so if you want to use that, just be consistent.