in terms of the national qualification framework...
GCSE = Level 2
A levels = Level 3
Bachelors Degree = Level 6
Masters Degree = level 7
PhD (AKA doctorate) = Level 8
(there are steps between 3&6 but you don't usually get a qualification at those levels if you're on a Degree)
it's sometimes possible to go directly onto PhD without taking a masters.
There isn't any qualification after Level 8 - fellow is like a lifetime achievement award for academics.