You definitely need a reservation for the Eurostar and as you have checked the availability of pass holder seats on b-europe then you know what the availability is.

There is a limited number of pass holder seats on each departure and that's why you still can buy full price tickets even though there are no pass holder seats. 

I have heard that Eurostar can release pass holder seats the night before the departure if trains not are sold out, but I have no confirmation of that. @rvdborgt @Al_G Do you know if that is true?

Just turn up: you will not even be able to pass gates as 1st step in the airline-imitation check-in process. They also do NOT have any office left there.

In FR it is even more hot and if you even see any news: heavy fires in the woods south France since many days and tourists forced to leave area.

thank you for the speedy replies!

In summary:

1. For Eurostar you should always book a seat reservation online.  Currently (August 2022) there is no call center support and no in person ticketing option in London
2. Your other alternative is to buy a full fare Eurostar ticket.  I expect I may be forced to do this to the closest point on the continent, and then I might travel via the Pass thereafter

Any corrections appreciated, otherwise leaving this for future question askers :)

thanks again for the speedy replies - happy to answer questions on American Amtrak in return 

You also have the option to go by ferry to mainland Europe from the UK?

Do you have a 1st or 2nd class Eurail pass?

Have you checked the availability of pass holder seats both to Paris, Brussels, Lille and Amsterdam?

thanks AnnaB!  

Stupid add on question from me: where do I search for the availability of the pass on https://travel.b-europe.com/dsb-rail/en/reservation-only#TravelWish? I did it before and can no longer find the option for the Eurail pass…  I found a helpful blog post from 2021 but the user interface has changed since then.

I have a 1st class.

I tried just Paris and Brussels, great tip to try the other options. 

For the ferry, seat61 says thats an 11 hour journey.  In this particular case that’s too risky/time consuming for my purpose.  

https://www.seat61.com/trains-and-routes/london-to-paris-by-ferry.htm

thanks!

The best place to see the availability of passholder seats on the Eurostar and make reservations is 

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

Press "later trains" and eventually you will find the next available connection. 

If you have a mobile pass you need to generate a Pass Cover Number in order to make the reservation at b-europe. You do that here in the PCN generator:

https://community.eurail.com/news-and-announcements-39/pass-cover-number-generator-is-live-5653

I've seen it a few times, a few days before departure. I don't know however under which circumstances they do that.

Two things here @AnnaB .

First is that there are no fixed passholder quotas as such. Passholder availability is connected to the regular fare brackets, once the regular fares sell to the point that the most expensive bracket passholder reservations are offered at is gone then no more passholder availability.

It does happen that they will open an additional train/s closer to departure and this will have the cheaper brackets to start with so new passholder availability.

I cannot say if they will sell passholder rates at short notice in person at St Pancras or other Eurostar ticket offices after the regular availability has gone, I would be surprised if they did this but unless someone tries… (and It won’t be me, I am far to far from London to chance it).

We did notice recently for some departures (on the following days) that pass holder fares were available but the corresponding regular fares were not. So there Eurostar did something special.

For the cases where we noticed, the extra pass holder fares were also available via the b-europe website. I posted some screenshots in one of the threads about it but I don't remember which one.

I have some informations about Thalys trains. Some users in Cologne reported, that it was possible to buy a reservation at a full Pass quota train on board of it, but asking Thalys staff before boarding. If it is also possible in Brussel, Amsterdam or Paris it is not known.

Similar experience on the tgv Paris-Barcelona which is also quota controlled. There were 10+ people showing up on the platform for a fully sold out train. They were allowed to board and pay the reservation on board while sitting in the restaurant. I suggest not to count on it but if you’re there at the moment it won’t hurt trying. Just make sure to ask the train manager before boarding! To avoid fines. Don’t just board without reservation on a train with mandatory reservations.
 

I was also allowed to board but my situation was a bit different as my Thalys was delayed and I missed a different train to Spain thé day before.

DO NOT GIVE THIS SHITTY COMPANY YOUR MONEY>