Does anyone know how much this journey would cost? I have been on the German De Bahn site which only has timetables and not prices. I couldn't see an English translator on the Croatian national rail site.
Actually, one more thing, what sort of weather can I expect in the region in September time?
Have you tried http://www.jizdenka.cz ? The site is usually very good at coughing up estimates of rail ticket prices in Europe.
Cheers! I'll give it a whirl. Its come up with 36 Euros for one way?!? Does this sound right?
Could be around that, definately not more. I have used this site for Sarajevo:
There you can see that the train from Sarajevo to Zagreb costs around 50 KM (~25 euro).
I've been on this route but I had a train pass so I don't know how much it costs, but take some food with you as there isn't a dining cart and it takes ages. It's basically like a local train, there were few people who got on at Zagreb and went all the way to Sarajevo, it was mainly full of those getting on and travelling a few stops before getting off. Weather in September as far as I'm aware can be quite warm but not as scorchingly hot as July/August, which is good because the train didn't have any air conditioning and it was like an oven (this was July last year).