BEagle - No need to bother the Belgrano, simply look at the ANO 2000, Schedule 8, Section 1.
UK CPL(A) - Privileges of a UK PPL(A) which includes an IMC rating and Night Rating.
UK ATPL(A) - Privileges of a CPL(A) without the restriction of public transport only in single pilot aeroplanes.
If you hold a valid UK CPL or ATPL you have IMC rating privileges. Why does everyone insist on making things more difficult than they really are?
The fact that the IMC rating should have been strangled at birth is another matter.