144,000_and_oneAdditionally, serving the defendants in this situation is not as simple as hiring a process server to serve them. It will require lawyers (and payment of lawyer fees) in every country where a defendant resides, as well as a thorough analysis of treaties that may exist between the countries governing the exercise of jurisdiction by Croatian courts in the other countries as well as an analysis of the relevant laws in of each of the countries where a defendant resides. This would be a very expensive feat to pull off, and based on the publicly available financial statements relating to his business that I was able to observe online, I don't believe that he has anywhere near the financial resources necessary to pull that off.
Exactly, to pull that sort of stunt off in the UK he'd need to hire solicitors and a KC(s) with expertise in both UK and Croatian law, (as you say) the various treaties & agreements they have between both countries and the emerging and probably fairly specialised legal knowledge around digital media.
You'd have to shit gold bricks to pay for that little lot in one country, let alone four or whatever it is.
I actually think Marc/Cora and Kim have a far better chance of suing him for calling them criminal liars all over social media (& I'm pretty certain on at least one relevent occasion when he was on UK soil).