The overseas number just goes to the same line as the domestic. One is an 0800 and one 0207 i guess its only really an overseas line because i cant use 0800 from Spain.
I´ll continue to try and update if i find a better route to contact.
I’d try sending a message to Monzo via social media if I were in your position. For example a direct message to their Twitter or Facebook. I’ve seen the Twitter team invite contact via direct message when people have taken to Twitter to complain about difficulties accessing support.