So which application is it that you are writing on?
You seem to come across all the questions that I had myself several weeks ago.

>>durchgestrichenen Kreis als Zeichen für "Durchschnitt"?
No, at least not in AE.

We use GPA, it's in LEO. ;-)

Yes, in BE.

I must add though: only in maths. In a student report, the abbreviation "ave." (for average) is commonly used. Then there is also agregate!

Es geht mir um die Angabe meines Abidurchnitt für eine Bewerbung an einer schottischen Universität.

As British universities are used to qualificatons being graded with letters e.g A B C etc it might be advisable for you to give your overall grade and a breakdown of the component parts eg English 1 Maths 2 etc since each course has different requirements regarding individual subjects. Hope this helps