1. A couple of flights would definitely be preferable to train-ferry-train for to/from Dublin. I don’t think you’ll be “missing out” on anything assuming you make some effort to do more than just visit capital cities. Day trips from London and Dublin or spending some time outside these cities in UK and Ireland should cover it.

2. I would use Eurostar, the chunnel train, to get between London and Paris/Brussels or Amsterdam. If will be significantly faster than either flying or the train/ferry combination.

Hi,
Yes, often (these days) it is cheaper and sometimes more convenient to take a budget airline for longer distances (esp. when you have limited time). MY first Eurotrip I had purchased a rail pass and in the end, I don’t think I really saved money (nor time). The other trips that followed I just purchased a bunch of budget flights and point-to-point train tickets. Sometimes there are more train options than listed on the sites (both price and availability options). A couple of things about the budget airlines:
1) HIDDEN or extra fees.
2) Book WAYYY in advance
3) There are other options besides RyanAir. Some are EasyJet, German WIngs, Wizz Air, etc. ALso, you can purchase 99dollar flight vouchers for a bunch of destinations in Europe (europebyair.com). You must purchase the vouchers before you leave the states. The good thing about this is the flexibility and no penalty for changing flights.
Happy planning!

And a note to OldLady’s post:
For the Eurostar train between London and Brussels I have used the 99dollar vouchers as well.

I don’t deny that sometimes taking a plane is better than a slower train or boat, but planes have somedisadvantages, too.

First, planes don’t go everywhere. The discount carriers cherry pick in that they provide service only to places that have a lot of traffic.

Discount carriers are famous for having restrictions on luggage, and they make a lot of money by enforcing them, and with other fees, so you have to be careful to research the carrier to find out what they allow, and what it will cost you if your pack is 1 kilo over their limit. I get the impression their target customer is someone on a weekend trip, with just a little black bag.

Trains go to the center of town. Discount carriers usually use a secondary airport or rent a field from a farmer, so you have additional costs, and time, to consider if you are going to a town or village. On a medium length trip, the flight time may look good, but when you add in time getting to and from the airport, baggage and security lines, and taxiing time, a train may be very competitive.

You miss a lot of scenery when flying. A train or boat has better views. I think everyone should take at least one trip by boat, just for the experience.

Discount carriers pack you in, and the only person you can talk to is the one or two beside you. Trains and boats have a lot more room, and you can move around and meet people and talk or dance in the aisles. My experience is that train stations have better food, and you can pick up some and have a nice picnic.

As someone who hates boats, I definitely wouldn’t recommend them. If you have ever gotten the least bit motion sick on anything before, you will hate boats too. They make motion sickness 50230238940293 times worse than other forms of transport. I love trains but the Dublin-Paris leg seems like a flight would be best.

I prefer the train to flying, but there are times, like this itinerary, where flying just plain makes more sense.

Other than a few truly scenic train routes, most of the “scenery” gets old after 4 hours. Further, most trains go so fast that anything close to the tracks is a blur and the distant view doesn’t change much. As for the “experience” of boats, I’ve been on numerous ferries and I actually enjoy them, but 8 hours of train-ferry-commuter rail to get from London to Dublin or 16 hours from Ireland to France is not my idea of a good time. I don’t recommend taking a ferry “just for the experience.” Most of the fast ferries aren’t much different than an airplane with an on-board McDonalds.

thanks for the helpful suggestions everyone, I truly appreciate the input!