Sounds like a fun trip!
In my very limited experience, you generally need to have filed a flight plan and report to ATC as required when crossing international FIR boundaries, at least this was necessary between UK <-> France and France <-> Spain when I did it as part of a group last year.
Language is generally English for major ATC services, but be aware that there are plenty of local airfields in France for example, and I would expect elsewhere, where knowledge of local language is necessary in the circuit and to have adequate situational awareness (the latter can also be true in bi-lingual enroute environments). I prepared a crib-sheet for my own use in France which you are welcome to look at for example
here (see also thread on this subject
here)
Moreover though, with so little experience flying on the continent, my urge and what I'd recommend would be to either team up with someone who has a bit more experience of this sort of thing to come with you or, failing that, to at least take another PPL along with you to halve the workload and learn together. Even things like the maps being different and not being as familiar with where to look up information will add to your workload.
Hope this helps - and good luck!
Andy
