Just note there are direct Eurostars from Amsterdam to London The thalys between Amsterdam - Brussels is wasted money as you either can catch the direct Eurostar to London or use the Reservation free Intercity from Amsterdam to Brussels Just note a Thalys cost abour 30€ per seat on top of the pass Eurostar 30-43€ depending on Route / Class 

Eurostar reservations should be done as soon as you can especially from Amsterdam as they operate from there only with the half of a train due the limits of the Immigration process in amsterdam. 

"Early fall” is kind of vague but for Eurostar certainly book as soon as you know which train you want to use. There is a quota on pass holder seats so they sell out before the train is full; during busy times that can be weeks in advance; Fridays and Sundays are also particularly busy. There are also direct Eurostars from Amsterdam by the way. Thalys also has a pass holder quota but there's an easy alternative: reservation-free intercity trains each hour from Amsterdam to Brussels.

There is no general answer to refund and exchange possibilities or for the possibility to upgrade to 1st class with a 2nd class pass. It depends on the train.

Eurostar and Thalys reservations can be changed once before departure time but there need to be available pass holder seats on the train you want to change to. Eurostar have a fee for that change, Thalys can be changed free of charge.

You can check Thalys and Eurostar availability here:

https://www.b-europe.com/EN/Booking/Pass#TravelWish

If you have a 2nd class pass, you can’t book 1st class in Thalys and Eurostar.

Thanks to those who responded.

I understand that the Thalys between Amsterdam and Brussels is unnecessary, but that is what our planned departure time pulled up, given that we will have to journey northward beyond London.

We will leave Amsterdam from Schiphol, and I noticed that the transfer between the Thalys and the Eurostar in Brussels is 48 min.--does this allow sufficient time for passport control? Or is the assumption this will occur before boarding the Thalys at Schiphol?

A final question--I am managing the rail portion of our trip for myself and my husband. Can I manage both passes under 2 separate profiles or is it better to manage each on separate devices? Thanks again!

What would be the final destination ? The first Eurostar of the day leaves Amsterdam at 07:47 or Rotterdam at 08:25 (arrival in London at 11:00). It is possible to leave Schiphol for Rotterdam at 07:10 for example.

48 min in Brussels is doable but remember that you need to pass all border controls there. In London you simply leave the train :)

Btw there is also a good daytime or overnight ferry between Hoek van Holland (Rotterdam) and Harwich. 30% discount with the pass and you save a night accommodation while travelling.

You can have 2 passes on the same phone but then you won't be able to travel separately (it might be needed once even if you don't think so).

Either way, make only one booking for seat reservations if you want to sit together. There are always better ways to book than eurail.com (extra fees + more expensive optional reservations). Have a look at :

https://www.seat61.com/interrail-and-eurail-reservations.htm

https://community.eurail.com/train-connections-reservations-47/how-to-get-reservations-105

The final destination is Scotland via York. We had booked our hotels already as we did not relish spending the night on-board a cramped cabin. We are near Sloterdijk so can either do Schiphol or Centraal departures. The 7:47, while attractive as we will get the passport control upfront, is a bit too early as we will still have a long journey to York. Per Eurail, 45-60 min. are required for passport control....will we be put on the later Eurostar if passport control delayed the boarding process?

Thanks for the tips about the other links--it seems we should be prepared for manual planning! :-)

Yes if the Thalys is delayed, you'll be put on the next Eurostar free of charge (whether in 1st class or 2nd class, doesn't matter). Don't worry : as long as you can make it to the Eurostar departure area (before passport control) more than 30 min before departure, you're guaranteed to take the train.

Actually for longer journeys I'd prefer leaving earlier as you can arrive earlier at your destination as well :)

There are multiple trains per hour between London Kings Cross and York. All long-distance trains in the UK have free optional reservations so on this busy mainline I'd recommend making one : through LNER website, there's even a seating map. For all other trains, you can book through gwr.com. Nothing will happen if you miss the train for whatever reason, just take the next one.

You're welcome and enjoy your trip !

Thank you!!! I broke the trip into smaller segments so we can leave at 9 vs the posted 10. This would give us ~2 hrs. for passport control! The UK leg is pretty straightforward in comparison! :-)

After taking the plunge and creating the various legs of the trip, I tried booking a seat.  I was directed to the Eurail site where I had to re-create the trip and add travelers and passes.  When I attempted to add myself with my pass number, I got an error message indicating it did not match on the app.  Why is that?  Should I get in touch with tech support???

I'm not sure what error that is but booking Thalys and Eurostar is easier and more reliable here:

https://www.b-europe.com/EN/Booking/Pass#TravelWish

With a mobile pass you just need to generate a pass cover number (1 will suffice):

As @thibcabe already wrote, the Eurail site is not the best booking site.