I have a UK ATPL(A)
ANO Schedule 7
The holder of an Airline Transport Pilot's Licence (Aeroplanes) is entitled to exercise the
privileges of a United Kingdom Commercial Pilot's Licence (Aeroplanes)
(1) The holder of a Commercial Pilot's Licence (Aeroplanes) is entitled to exercise the
privileges of a United Kingdom Private Pilot's Licence (Aeroplanes) which includes an
instrument meteorological conditions rating (aeroplanes) and a night rating
(aeroplanes) or night qualification (aeroplane).
Besides which, the UK ATPL does not contain the limitations found in a PPL that the IMC rating is designed to get around.
to fly as pilot in
command of an aeroplane without being subject to the restrictions contained
respectively in paragraph (2)(c) or (f) of the privileges of the United Kingdom
Private Pilot's Licence (Aeroplanes)
But if per chance your ATPL is a JAA Licence, you don't have the privilege as stated.