Got this email today. They're asking me to change a LHR-MAD flight from the last one on Monday to one at 11am on Tuesday for a 71 euro voucher. I can't do that, so can't add a data point on whether the links work.

On a related note: I assume that using such a voucher to offset the cost of a future flight doesn't change the Avios awarding, but knowing Iberia I wouldn't put it past them to not count it!