I haven't done an AUP in well over a year, maybe two, so things like opup rules may have changed but whenever I did, I would always check which seat I would get before agreeing to the offer.

Sometimes that was a simple conversation - "I can offer you X, Y or Z" and I'd be happy with that; other times there was a little more negotiation involved. Occasionally I declined the AUP (if I couldn't get a window for example) and then after a phone call I would be offered one. I did this maybe a dozen times and I don't remember being unsuccessful (either paying for a poor seat or choosing to stay in WT). But it was a while ago now.