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

Only Eurostar has a passholder quota. Check London - Lille if London - Paris is sold out. If you mention the travel date I’ll gladly have a look too.

(Also possible to reach Munich via Brussels but it takes longer.)

For all other journeys availability is less of an issue: no quota and plenty of alternatives. :)

Thank you Thibcabe! That is very helpful to know. 

I am now looking at Paris to Stuttgart and receive this message: “Seat reservation has to be done at station.” I presume that means I can only buy the ticket on the day - but is it possible that I wouldn’t be able to board the train if it is full? (I’m traveling with someone who doesn’t have an Interrail pass and will have booked this journey in advance so that would be awkward!)

I have tried looking this up online but can’t seem to get a clear answer so any help you can give is much appreciated. 

Where did you see that message? For what date and time are you trying to make a reservation?

Hi Anna, thanks for your reply! I saw it on RailEurope. I’m trying to book for 24 July at 10.52 from Paris. I also tried to look up the journey on b-europe but Stuttgart and Munich don’t seem to be in the list of stations.

Rail Europe has been acting weird lately. Later trains that day are available but not that one…

I'd try again in a day or two. This train won't sell out so far in advance and there are plenty of alternatives anyway.

Thank you again! One last question - for now! - On Rail Europe I am getting this message for the Eurostar I want to get back: “Rail Pass doesn't apply for this trip” and on B-Rail it is also appearing at what looks like a full price. Is that likely to be because the pass allocation has run out? 10 August 19.11 from Paris to London.

Yes indeed. With the Olympics ticket prices are artificially very high and thus passholder reservations unavailable. Basically when ticket prices are over 170€ or so, there are no passholder fares. It's rather annoying.

There might not even be a single passholder booked on that train but that's the way it works! :/

The alternative is to travel from Lille-Europe to London. Plenty of departures that day (make sure to book well in advance).

If you're doing Grenoble - London that day let me suggest this route avoiding the Paris hassle (especially considering all the extra security measures for the Olympics):

- TER Grenoble - Lyon Part-Dieu fairly frequent

- TGV Lyon Part-Dieu - Lille-Europe 10-20€

- 1h break for passport controls, etc. (longer stop if you'd like to visit a bit)

- Eurostar Lille-Europe - London St. Pancras 30€

Thank you Thibcabe, that is amazing advice - it looks like a much better journey!

I wonder if you might have any further thoughts about the Paris to Stuttgart connection I’m trying to book where Rail Europe says you have to reserve at the station. When I try to book through the Interrail app it shows as bookable but then says ‘Sorry something went wrong’. I can see there are seats available still to buy normally. Do you have any idea how I could move forward with that situation?

No idea honestly.

I can get to the payment page on interrail.eu. Does it fail at the next step?

Otherwise I’d wait a bit as it seems strange.

Thanks once again! Eventually, it worked this morning after trying 3 days in a row on different sites and it didn’t work. I have the reservation now so that is fantastic. Your help has been very reassuring - thank you