What train are you trying to book? (Route, date, departure time) There may be simpler and cheaper ways of booking.

It's new to me that you would need to indicate the place of issue of your passport to book anything.

I'm trying to book the reservations shown in the screenshots above. Any advice welcome :)

14/2 Milan-Venice: book via tickets.oebb.at and save €4. Do NOT use "Seat reservation only” but add the Interrail/Eurail discount and then look for normal tickets.

17/2 Venice-Rome: book via tickets.oebb.at and save €4.

20/2 Rome-Genova: I'm not sure why you're travelling via Naples. There's a direct train Roma Termini 18:27 - Genova P.P. 23:20 (book via tickets.oebb.at for €10 per seat). The night train leaves Roma Ostiense at 0:14. You can save €3 by booking the night train via Italiarail.

22/2 Genova-Ventimiglia: Use a reservation-free regional train. Or book via tickets.oebb.at and save €4.

23/2 Marseille-Nîmes: there are direct reservation-free regional trains at 8:23 and 23:22, taking 1h 15 min, and save €44.

24/2 Carcassonne-Narbonne: just take the reservation-free TER at 18:20, arrival in Narbonne 18:51, and save €44.

24/2 Narbonne-Barcelona: book by phone via SNCF and save €4 (press #85 for English; reservations are sent via email). Or travel via Portbou using regional trains, eliminating the need for reservations entirely.

None of the booking methods above require a place of issue for the passport. ÖBB don't need many details at all.

Thanks so much the Rome - Naples - Genova anomaly is an error, so glad that I posted it! We're visiting Pompei for the day before heading north.

Re your first question just answer as printed in your passport. Originally UK passports were indeed issued from offices identified by their location, but now some of them are identified by their issuer (HMPO His Majesty’s Passport Office).

The prices the shots show are for full fare and for 2-not for the RES as such. And as rian already explains: most of them in FR can easily be changed to local TER trains without even the chance to RES-just as about any local GB train in the South West.

For those in France, if you do want to travel on those services with compulsory reservations, note you can get these sometimes for €10 per person when booking directly from SNCF on the phone, or with an additional €4 booking fee (still €20 cheaper) through https://travel.b-europe.com/Eurail-GE/en/booking-tgv

Eg: Marseille-Nîmes

I am surprised it asks for the place of issue of the passport. Seems to occur when reserving the Italian night train. 

For that one: reserve through the Italiarail page linked above and consider getting a 2-person private sleeper cabin (€56 per person) instead of two couchettes (not really beds) in a 4-person couchette compartment which you'll share with others (€39 per person).

Thanks to all for the fantastic advice above, collectively you've saved us nearly €200 and ensured we'll have a comfier journey on the night train as the options for booking that through interrail are limited :) 

Just a follow up query if I may: I am attempting to book the night train on Italiarail and it asks for a passholder number. I assumed this was the 6 character pass reference visible on the rail planner app, but the website doesn't accept this. What number are they looking for here?

Italiarail expects a pass cover number, which is on the cover of a paper pass and (for Interrail) consist of a capital i and 8 digits. For mobile passes, you can generate one: