Originally Posted by corporate-wage-slave

In law the downgrade is down to the operating airline, Iberia, this entitles you to a reimbursement under the Mennens formula, see the EC261 thread for all the details on that, with Mennens linked in from the wiki. The complication almost certainly both airlines will want BA to handle this, since they are sitting on the ticket funds, from which this will be paid, as opposed to EC261 compensation which isn't ticketing related. It won't be a lot of money, but you best to a rough and ready calculation yourself. I think I would approach BA first on this, if they drag it out or give daft answers then MCOL both airlines. Note, do NOT ask for compensation for this, since they can and will decline. The bag will arrive in a few days. If you are home now then that's it really, usually the full remedy is to return your bag in the next few days, via DHL.