There aren’t quotas as such.

Passholder reservations are available until the general fares reach their highest 2 or 3 fare brackets, at which point no passholder reservations are bookable on that train.

The fare bracket prices remain fixed but they can and do vary how many seats are available to each band based on expected demand.

Edit: This is the arrangement for Eurostar to/from UK, for ex-Thalys Eurostar services it is a variable quota that they set for passholders.

You can check (and already book) passholder reservations through https://www.b-europe.com/EN/Booking/Pass#TravelWish

It indeed works by buckets. Usually the quota sells out at 170-180€ per ticket per my experience.

I don't know if it's the case here : sometimes Eurostar does not release tickets until 6 months or less due to possible change in timetables (because of works mainly).

I see loads of pass holder seat availability e.g. on 14/15/16/17 July.

If you don't then please mention your travel date and the number of seats you need.

Thanks all for the helpful responses - much appreciated. I did not know it was possible to check and book passholder reservations through https://www.b-europe.com/EN/Booking/Pass#TravelWish - v useful info!

I am looking to travel from London to Brussels the morning of Friday 12 July, 4 seats required. Using the b-europe.com site I can see that there are seats available on the 9:01am and 7:04am trains, but as expected nothing for the 8:16am train which is the one sold out on eurostar.com.

Thanks again.

Since this train shows as not available in all classes (incl. the always available Business Premier) the likely reason is works planned somewhere in the Netherlands (it continues to Amsterdam) = train not on sale yet.

I'd wait a few weeks and see what happens. Check regularly the website.

Thanks a lot @thibcabe, good to know.