Thank you! I booked it at end of November, as a basic economy, hand luggage only plus I added seats. I didn't ask those questions but have gone onto manage my booking and there was only a fee to amend the one way flight, but not letting me add in another flight.

Ideally I'd like to get the sale price for return flights if I could, even if I have to pay a little bit more to do so. I'm currently in Australia so limited to texting at the moment.