Thanks both!
He's 18-24months. Abandoned in a village near to the rescue.. they don't know why he was abandoned but it's pretty common over there. Mostly 'we were bored of the dog', or 'we can't afford it'. They reckon he was treated pretty well as he's good with doggos/humans, used to house life, chilled and confident.
@DougNg - in the current situation yup, given most borders are closed. But usually fairly easy within Europe.. pet passport, list of vaccines and checks - they can then travel easily. The shelter usually does a road trip with 15-20 dogs at a time every 6-8 weeks. The usually do it over 3-4d, but the last trip (2 weeks ago) back from UK to Bulgaria took 7-8 as every time they hit a border it was in the process of closing down due to COVID19. So yeh.. could be a few months before he makes his way over!