Hi Toni,
Yes, I have been waiting for another colleague to come back to me on one of the holidays you highlighted as the system I usually use doesn't have this information listed.
WiFi access is still quite variable depending on where the tour is, so it's always best to check.
For the Cilento Coast the hotel has free wi-fi in public areas and also in the rooms (you will just need to get a password from reception to use it in the rooms).
I have chased for the information about Athens, Olympia and the Corinth Coast and will come back to you on this.
Kindest regards,
Jules (aka Julia)