1. No, but there are some situations where it can be very helpful. There are some old posts about it in the “packing” forum, or repost this question there, for more discussion.
2. Fly is the best option from Ireland to England. Try Ryan Air for cheapest and check www.whichbudget.com to see which budget airlines fly which routes. See out “cheap flights” forum, particularly the new users thread, for more search engines, tips and help. Ferry is a good option between Croatia and Italy, although I’d check flights, too. Ferry is also an option between Italy and Greece, but I’d probably fly unless I wanted to spend time on Corfu. Train from Florence to Bari or Brindisi overnight ferry to Patras and train or but to Athens makes for a long couple of days.
3. Probably. Most European nations are members of the Schengren Agreement. You can only spend 90 days in any 180 day period inside the Schengren area, so unless you can find a way to spend a full three months in non-Schengren member countries, it will be hard to get by without one or more (perhaps several individual countries????) visas. Check the visa checking tool sticky on the “cheap flights” forum and some old posts in “packing.”

Etc. London to Brussels is best by Eurostar, the chunnel train. It’s faster than flying and much more comfortable. Consider time in Brugges in addition to or instead of Brussels.

Check the thread pinned at top of our Cheap Flights forum next-door, titled “nifty visa-checking tool.” Insurance is technically required in most cases, but probably not enforced unless other red flags come up at your arrival entry interview (which you will get in the UK at least). Insuremytrip.com might have something if needed.

Be sure you’re not overstaying your allowed tourist days! I can’t tell how many days each place on your itinerary, but looks like with 6 months, you might have more than 3 planned in the Schengen Border. US citizens only get 3 months to play tourist there, up to 6 months UK, and up to 3(?) Ireland. So Schengen is the potential sticking point. You can’t leave for a day and return with a fresh 90 days; it’s 90 days in/ 90 days out. The visa checking tool will show you requirements for each border you’ll enter (UK, IE, and Schengen).

Ireland, the U.K., then a flight to Croatia will help maximize your time in the Schengen zone. Have you already bought plane tickets?

When you enter a Schengen country, you start a six-month period. During that period, you can stay up to 90 days, without going through the formalities of getting a visa. If you leave the zone after 45 days, you can return for another 45 days within the six-month period that you started when you first entered. You can’t get another 90 days until you enter after your initial six-month period has expired.

You can stay 180 days if you get a Schengen visa from one of the member countries, and during that 180 days you can travel among the various Schengen countries, so you don’t have to get a visa from each country. The Schengen visa can be obtained from an embassy of any member country, and requires you to visit the embassy with certified documents, a passport that won’t expire during your visit, and some money. Its a bit of a hassle because there are so few places where you can file your application, and it takes some time.

For further information, and even a copy of the application, do an internet search for Schengen visa.

Wow thanks so much for all this extremely helpful info! The Whichbudget site is awesome.

I did some additional research on the “nifty visa tool” and came to the conclusion that our trip may not be possible since we are basically going to be in the Schengen for more than 90 days. I concluded this since a “long stay” visa does not mention anything about tourism, it’s for studies and residency. Then I came across a “working holiday visa”. Where could I find info on how to obtain this type of visa?

Such a bummer that it’s not possible to stay longer than 90 days in the Schengen zone, because virtually ALL of the countries we want to visit are in the zone! arg!