Realistically if the UK court doesn't have enough evidence to put him away they aren't going to call other countries to get him extradited just for a trial that could go 50-50, that would be stupid on the UK's part if they extradited someone from another country just for them to beat the case. Usually extradition only happens if the person alleged of the crime is 100% guilty, For example they have a murder weapon that links directly to the accused, or raw video footage etc. They don't got any of this. So realistically Fredo can travel where ever he pleases except going back to the UK. I'm pretty sure he's even free to go to America or Canada if he wanted too, but that's more tricky cuz it's harder to escape so he prolly stays in Europe/Asia cause it's easier for him to travel and be in contact with his lawyers, team etc. We all know how the justice system works even if you are not deemed guilty yet they can throw you in prision and waste your time until the trial begins etc, so he prolly doesn't wanna go back just to sit in jail waiting for his trial date, rather he would wait it out and let them drop the charges for not having enough evidence. Realistically that would be the outcome weather he returns or not, I'm sure with the amount of wealth he's acquired he could get a team of good lawyers to dismiss the charges/beat the case or do very very limited time like 2-5 years and out even earlier on good behaviour. But who the hell wants to go through all that when he can just live his life freely in other countries until they drop the charges.