You can fly on Wizz air from Luton in the Uk, and they are very cheap. To fly 2 adults, return, cost £70 including tax.

When you land in Zagreb, you head to the main entrance, and the airport buses all go to the main bus station in town.

When there, you head down to the huge bank of booking booths. If the person there speaks another language, it is usually displayed above the booth.

There are a number of buses every day that head across to Opatija. Most of them head through the town of Rijeka, so just look for this name and the bus is sure to head to Opatija.

One thing that is not common in Croatia is English speakers, apart from in the main hotels. A little German or especially Italian would go a long way!