Specifically Toulouse to Tarragona. We're open to any suggestions on how best to travel between the 2 cities.
When will this be? This sprint RENFE will start a Toulouse - Barcelona service, so then getting to Tarragona by train (with a change in Barcelona) would be easy.
It will be in March. Do you know of any other options?
You can still do this by train.
You can book Toulouse - Barcelona on www.sncf-connect.fr. There are several trains per day, and the trip takes about 4 hours. You will have a change in Narbonne though. (but changing trains is a normal and expected feature of train travel).
Then from Barcelona just take on of the half hourly local trains to Tarragona. (The same train you would take if you were to eg. fly to Barcelona...).
I am currently seeing prices around 50,- for that route, so it is good value.
Alternatively you could book the once daily Narbonne - Camp Tarragona train on www.renfe.es, and add a Toulouse - Narbonne SNCF train. That would mean depart Toulouse 8:43m arrive Camp Tarragona 13:21. Trainline can book that for you.
My choice would be to book on SNCF to Barcelona as that avoids a inter-carrier change to a once a day train... Once in Barcelona you have multiple options to get to Tarragona. The regional trains you do not have to book in advance...