Hello ​@Ricky Rails 

Usually no reservations are required or possible for the TER in France, but some exceptions are possible, for example the TER fluo Paris - Troyes - Mulhouse or Paris - Châlons - Strasbourg. But note that TGV reservations are not expensive, from 10 € if you reserve in advance. You can obtain a full refund if you change your plan.

For the TGV, Intercités and TER in France, you can reserve seats on raileurope.com. 

I don’t have any experience in Spain.

In France, most TERs are reservation-free. Exceptions are TERs between Paris and Normandy and on Paris-Strasbourg/Mulhouse. In those cases, reservations are mandatory only for journeys from/to Paris and not for other journeys. SNCF however have implemented this incorrectly in their timetable data.

There are also a few Intercité routes with only optional reservations.

In Spain, Cercanías/Rodalies and some regional trains are reservation-free. In Catalonia, also MD trains are reservation-free. Some routes can however only be done with a reservation. In such cases, look for MD trains (€4 reservation). bahn.de or the DB Navigator app usually give the correct indication whether or not reservations are mandatory. Cercanías/Rodalies timetables however are not in there because Renfe doesn't share them. (DB label MD trains as IR for some reason.)

Thanks, Danhiel and rvdborgt,

( I had to create another Community account as I forgot password to Ricky Rails, now it’s Ricky Rails 2 )

Appreciate your replies, I kind of understand...TER in France largely seat reservation not required, Intercitie’s some without, most with seat resrvations…

Spain I think, yes, Cercanias / Rodiales local services not usually required but form Regional, Largo Recorrido, etc. ( not AVE ), probably require some seat reservation…

Fees can vary from minimal to more…

It is still quite confusing, I think, to plan or use Interrail global pass travel : depending on which provider or agent website used, this can be clearer or not...Interrail / Eurail website charges extra admin & booking fee on their site it seems, and may cover only the main high speed lines..?

I looked at the more obvious TGV / AVE combinations to travel into Spain from UK, via France, and yes - not wildly expensive, but seat reservtion fees of approx 23 / 35 Euros for TGV journey e.g. Paris - Beziers / Barcelona.

Then fees approx 15 / 25 Euros on AVE trips onward within Spain…

I guess an alternative is if you travel spontaneously and with plenty of time on the non high-speed trains, perhaps just booking trips at each stage / station en route, where you can check route eligibility / pass validity / seat reservation fees with station staff but this would be a slower pace of travel ( which is also part of the enjoyment, to travel cheaply and freely, seeing places...)

However, shorter duration passes and for longer, faster journeys be prepared to pay the extra costs on TGV / AVE…& indeed EuroStar ( London - Paris - London seat reservation available at £ 30, limited quota )

I did some research via RailEurope site, comparing tickets for travel in advance : spring 2025, and there are quite reasonably priced fares available if you search a variety of different dates, so for example LONDON - Paris - South of France ( Lyon or Narbonne overnight stop ) - BARCELONA - ( via Madrid ) to SEVILLA, then return : SEVILLA - MADRID - Valencia - MADRID - ( via Barcelona ) Paris - LONDON with tickets by stages or straight through, depending on where you want to spend time en route...APPROX £ 400. This cost ost could be a bit cheaper or approx similar to the same routes / stages on a 15 day Interrail Global Pass with extra seat reservation fees…£ 305 on currennt 25% discount plus £ 100 / 200 of extra seat reservations.

And yes, I found the Man in Seat 61 website also very informative.

Let’s see what works out best...

Yeah, you’ve summed up the most essential information indeed .

Passes are not necessarily the cheapest option, but you’ll get flexibility in return.

Only Spain is the worst on seat reservation level, seconded by France/SNCF and related companies like Eurostar. I never suggest them for Interrail/Eurail beginners since they take away a lot of the flexibility that makes it so nice to use a pass.

Best countries for spontanuous on the go decisions: UK, Belgium, Netherlands, Luxemburg, Germany, Austria, Switzerland, Denmark

Average: Seat reservations needed, but not a big deal as trains are frequent and rarely sell out and/or have only a modest fee: Eastern Europe, Sweden, Italy

I’lld suggest when going for a pass: book your Eurostar London-Continent or the other way around, and cross border TGV and AVE’s to Spain.

Otherwise you’re perfectly fine reserving trains 1 or 2 weeks in advance in Spain and France as your plans progress, to be cut even shorter to only a couple of days if you travel off peak during weekdays far away from a holiday.