Actually, it was confirmed in their investment deck for the latest crowdfunding round, that Monzo are planning to expand to Europe -
https://community.monzo.com/t/card-availability-geo-limited-dont-hold-your-breath/7392/19?u=alexs
& the USA -
https://community.monzo.com/t/american-version-of-monzo/6868/5?u=alexs
Unfortunately that doesn’t help @anon94910376 much though 
So for now, it’ll only be UK users who can try out Monzo while travelling in Barbados 