No-that is becse each&every newbee all seem to want to use exactly those trains that are hard to get. That the Brits need to go out on €* if they feel they should do it all by rails is their fault of living on an island.

Its daft simple-without any worries, if you choose a different route.

The app can even be set to ´NO REServ needed´ and then just see what it spews out.

OR use the other manual by seewulf on howtodo via other ways. And no-most trains are not fully booked weeks advance-very much like in that GB too (unless they do the thing they like so much also there:strike and inconvenience the public)

A Eurostar seat reservation is 30€. There are many trains without reservations but this very much depends on where you're going. There's a whole section on the website about them. Spain, Italy and France are the least Interrail-friendly countries, where you need reservations for most or all long-distance trains. In France and Italy, there are often slower, reservation-free alternatives; in Spain that is not always possible.

If you want to travel with less hassle, go to the Benelux, Germany, Denmark, Switzerland, Austria, Czechia… most trains there can be used without reservations. and optional reservations are inexpensive, especially if not booked via Interrail.