Those are some long journeys.

Sofia - Milan will take at least 2-3 full days. I’d fly or skip that city if you’re short on time.

Milan - Barcelona is also 2 full travel days but you could spend the night around Nice or Marseille. Not too bad and beautiful scenery guaranteed!

Barcelona - Amsterdam is doable in a long travel day via Paris. High-speed trains on that route are extremely popular so you must book as soon as your dates are set.

Do you have fixed start/ end points and want to do it in that order? Because it might be more logical to change things around a bit

Certainly, I’d suggest flying at least some of it.

How about starting in Sofia, and flying to Milan first.

Milan to Brussels or Amsterdam can be done in a day, but better over two days. Again, there is a sleeper option, from Switzerland.

Brussels-Amsterdam is just a couple of hours, direct.

Amsterdam-London is 4 hours direct.

Then you could pick up a cheap flight to Barcelona, or alternatively take the train all the way. It’s another all-day journey

Hi,

Thank you for the response. 
We are flexible in terms of which city we visit first. The only thing that is fixed is our final destination (London). I am just trying to avoid making too many train changes between the above destinations. Will also consider taking fast/sleeper trains. I am aware we have to pay reservation fees on some trains.

Thank you

What is it that puts you off connections?

Is it's the physical hassle, we can recommend journeys with easy changes. If it's the risk of missing connections, we can recommend strategies to mitigate that (choosing longer stopovers and/ or choosing routes where you only have to. wait an hour is lf your mood a train.)

The only journeys among those that would be direct are London/ Brussels/ Amsterdam

Good morning,

It is purely the physical hassle of changing too many times, but I would appreciate if you could suggest easier changes/routes. This is our first time using trains in Europe, and with kids, so please forgive my ignorance.

Earlier, I should have said the only fixed places are our starting point (Sofia), and ending destination (London). We are flexible with the remaining destinations. At the moment, we are thinking of flying from Sofia to Barcelona, and use trains for the rest of the journey. 

Finally, would a 5 days global pass be enough? would you recommend first class or do you think second class will suffice? 

Thank you again.

Well the number of pass days depend on your plans. Second class is very busy in summer: for more availability and quieter carriages I’d recommend 1st (but 2nd is fine too!).

High-speed trains out of Barcelona and Eurostar services to London are very popular, you shouldn’t wait too long to book those. For the former there are alternatives, not for the latter (except bus/plane or ferry).

Changes are easy most of the time and as long as you leave sufficient margin it will be fine. It’s much more exhausting to travel for 12h continuously than to change 4 times trains!

Make sure to leave 30 min or so between high-speed trains (but again depends on the specific route!) while a 3 min change in Switzerland is guaranteed to work.