For anyone planning on flying Air Asia, please try to get some Malaysian dollars even if you are not spending any time in Malaysia. It is much cheaper to use Malaysian dollars on the plane for snacks etc... than to use Australian dollars. $100 will give you about 300Malaysian dollars.
Ok the plane was pretty normal and the food was good, the tvs are hand held and cost about 30 Malaysian dollars and you can watch for around 4 hours (or however long the batteries last). The food and drink is reasonably priced, however I do suggest booking your meals when you book your tickets (it is cheaper).
If you do spend the night in KL before flying off to the next destination I suggest just staying at one of the hotels near the airport like Tunes Hotels. We didn't and ended up having to pay $50 return in the taxi to the house we were staying in. Although it was a nice place to stay.
From KL to London again use Malaysian dollars and keep the left overs for your return trip.
Also when booking your flights only order the comfort kit once per person you can take it with you on the other flights (blanket, pillow and eye mask).
If you have travel insurance do not pay extra for the insurance on the flights.
I would fly with Air Asia again with no worries.