VM44:
As you rightly point out A-Levels stand for "Advanced Level", whereas O-Level stood for "Ordinary Level". Both of these grades were under the GCE system. Though GCE was usually synonymous with O-Levels, it has now been retained just for the A-Levels.
There were also the AS-Levels (Advanced Subsidiary), but I don't know anyone who went for them, unless they were certain they were going to flunk the A-Level and wanted to fall back on having at least some grade..
I think I got about four or five O-Levels under the GCE (General Certificate of Education) system.
CSE's (Certificate of Secondary Education) was a lower grade still, of which I got a further three.
They were replaced with the GCSE (General Certificate of Secondary Education) system.
Confused? So were we!
It mapped out like this:
GCSE / GCE / CSE
- A / A / ..
- B / B / ..
- C / C / 1
- D / D / 2
- E / E / 3
- F / U / 4
- G / .. / 5
- U / .. / U
Where "U" = Ungraded = Fail