There is a big European-wide timetable change on 10th December. Most tickets after that date are not yet available except Eurostar and SNCF.

Interrail/Eurail have some extra limitations so they're not offering passholder reservations either. However you can use this website of the Belgian Railways (4€ fee per order compared to 2€ per person per train on eurail.com) : https://www.b-europe.com/EN/Booking/Pass#TravelWish

I'd recommend booking Eurostar quite in advance around Christmas, especially if you need to take a specific train. Most trains are still available but the route is really popular and there's a passholder quota... :)

(Another tip : it is cheaper to avoid eurail.com ti book seat reservations mainly due to extra fees but also unreliable info. Don't hesitate to come back for further questions.)

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

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

Thanks for the detailed answers! Never knew about the timetable change… haha 

I see that the Belgian website does have the option to choose the eurail pass type. will it still be the same reservation process as booking thorugh the eurail reservation? 
(by this, i’m referring to things like will the reservation still be counted as ‘using’ the eurail pass & will ticket be added to my eurail app?) just a little bit worried about the possibility of having to book a separate ticket without actually using my eurail pass.. :(

The reservation will never appear ‘in’ your Eurail app. Reservations are totally separate from your app, which is the ‘ticket’.

B-europe will give you a reservation by email, including a booking reference. You can put this booking reference into the Eurostar website, and choose your seat, then print it off to show at check in. (I just add it to my apple wallet)

Thanks for the clarification! 

Cuz im using the 5-days flexi pass, i believe once i book my tickets with all my eurail details entered, they will (somehow) keep the record that 1 out of 5 days of my pass is used. 

Appreciated on your tip to use the Apple wallet :) 

Yes, when you activate your first train on any travel day (no need to do this until you’re in the station and sure you’re travelling) it will mark that you’ve used up 1 of 5 days.

So, on the b-europe site, it's allowing me to make a reservation from London St. Pancras to Brussels in July, but not the return, in August.

Do I:

a) panic, and buy a plane ticket back to the UK for August

b) wait til after Dec 10th

c) try another website??

You are way too early !

Most trains can be booked 2-3 months in advance but Eurostar is an exception : usually 6 months, sometimes a bit more than that.

Use B-Europe in a few weeks to buy all the trains in a single booking (to save fees). I wouldn't worry about it until January or February frankly. Trains won't sell out until max 2-3 weeks before.

As an example : trains in the UK are often released 8-12 weeks before travel date, sometimes even less.

Ok, phew! That's really helpful, thanks. 

As you suggest, I will go back to B-Europe in a few weeks!

Thanks again, Richard