>At the end of Iron Man 3, didn't Stark renounce being Iron
>Man? (Or have I completely misinterpreted the end of that
>film?). I thought part of AOU would have been about him
>making the decision to put the suit back on but there wasn't
>really any mention of it.

Avengers tower is in New York, he was living back in Malibu when IM3 started, so likely he had some suits in tow.

And notice how after he threw the arc reactor into the ocean, he drove away TOWING his machine? I think the whole point was, as long as he lives, Iron Man will as well. Lord knows he can build a suit out of anything.

And keep in mind that there was still a SHIELD in place up until TWS. At that point, and with Hill going to work for Stark Industries, I imagine that Tony was brought up to speed.

And even though he wasn't at the helm anymore, Fury said to Hill at the end of Avengers that they would come back "because we'll need them to."