Find a ferry to Croatia
It is quite difficult to deal with Jadrolinja ferries from Britain - so I recommend a London company that will book Italy to Croatia ferries on your behalf: telephone 00 44 (0) 8704 10 60
I recommend using the following three sites to get an idea of the cheapest flights for your dates and destination.
1) If you cannot decide on which part of Croatia to visit try Skyscanner.
In the Flight Search box, enter where you want to fly from, and your dates. Click "everywhere" in the "To" list then type in "Croatia". As long as there are flights available to Croatia in your chosen dates, Croatia will appear as a choice, and the next screen will give you a breakdown of the flights available in those dates by price and airport. http://www.skyscanner.net/airports/airports-of-the-world.html
You could leave it there but if you want to research further use the following list to double check all the airlines flying from the airports of your choice...
