Nikos, what is important in not specialising your studies from that early level, but what are you going to go into, later on, as a professional. I mean Zaha Hadid 's 1st degree was in Maths and Santiago Calatrava graduated as a structural engineer.However, they both work as architects now.
"You are what you claim to be"
Of course, your studies should be relevant to architecture.
Architecture is a very wide subject and it might not be good to limit your choices by choosing something so specified as "architectural and civil engineering"
I suggest that you choose a course with code K100 in a very good school.
After you finish your part 1, you will be able to decide what EXACTY you would like to focus on.That is because your interest in architecture will grow during the first years of your studies and you will find that you are interested in stuff you didn't imagine you would be, in the first place.
I know people who studied architecture and went into town planning, 3D design, sociology, crime & control, fashion design, photography, journalism..
Architecture is not strictly about studying structures & constructing buildings.
In the UK, architecture programmes vary greatly between schools, but in general they are more design than technically orientated.
Another suggestion would be not to return to Greece after your studies, because aside DOATAP, you would waste your time and great career opportunities.
Let me know if you need further advice...