Actually, looking more carefully at my licence, it lists the following:
ATPL (A). With a date and then GBR
CPL(A)
PPL(A)
So it may be that the licence is just an ATPL(A), because the CPL and PPL lines do not have a date beside them. I presume I can fly a Cessna under the privileges of my ATPL(A) once I have an SEP rating added?