Suggest you get familiar with the CAA SRG's website. Chock full of info.
LASORS Book mark this one.
Ref
Section G
The holder of a valid JAR-FCL CPL(A)/IR with
JAR-FCL ATPL Theory credit will be credited
the JAR-FCL ATPL(A) Theoretical knowledge
examination for a period of 7 years from the
last validity date of the IR(A) entered in the
CPL(A).
Ref
Section J
A pass in the ATPL theory examinations will be
accepted for the issue of a CPL or IR during the 36
months from the end of the month of the date of
the final pass in the examinations. Provided that an
IR is obtained during this period, a pass in the ATPL
theoretical knowledge examinations will remain
valid (for the purpose of ATPL issue) for a period of
7 years from the validity date of the most recent
renewal IR entered in the CPL. However, if a
professional licence with IR is not gained during the
36 month period, the ATPL theory credit will lapse.
Candidates would have to re-pass the ATPL or IR
theoretical knowledge examinations before an IR
could be granted.