Some questions (vocabulary)

[Emanuelli]

Hello, can anyone help me understand the following sentences???

a) New Zealand has many advantages over Australia, the main ones being that it's smaller and cooler. (What do the words in bold mean???)

b) We'll have dinner at 8.00, shall we? (Why was "shall we" used instead of won't we???)

c) In a C.V. there was the following information on Education. Please, help me understand what is in bold.
Watford Grammar School
8 GCSEs
3 A- Levels
Bristol University
BA (Hons) Psychology and Education

Please, help me. Thanks.

[Casiopea]

a) . . ., the main advantages being\are

b) We'll have dinner at 8.00, shall we? <Polite suggestion>

c) GCSEs: General Certificate of Secondary Education (British)
Hons: Honors