As i have to fix a child seat in my Eos, i know it has an Isofix system. Would anyone know if it has the "top tether" system as well, namely a third hook somewhere behind the back seats which holds the child seat apart from the two Isofix ones? (i think there is no "top tether" system in the Eos though)

Not sure what that system is im afraid. I have a fixed car seat for my daughter which is not the isofix system but is held in place with the seat belts. The seat is a Britax Ascot seat.

Regards Trish