"Special offer of an extra 9,000 Avios for each ticket purchased between 21 and 24 June 2018 (maximum of 90,000 promotional Avios per member) on iberia.com for a flight operated by Iberia, Iberia Express or Air Nostrum. "

The T&C are pretty clear. If Iberia choose not to credit the Avios - no idea what they will do to be honest - on what grounds are you challenging the transaction exactly? You have an ticket, and you haven't bought via the website. Might be some mileage in challenging via distance selling regs but I can't help feeling you'd need to cancel now, pay the £15, and try to claim that back rather than refusing the cancellation offer. Cooling off is about cooling off, not having your cake and eating it.

IB have about a week to figure out what to do if this has backfired before having to credit Avios. I would think that applying strict T&Cs is an obvious thing to do, and there will probably be records about where bookings originated. So a quick line of code to exclude app made bookings and you're shafted.