If you hold an ATPL with 3000 hours on aircraft above 30,000kg talk to CAA.
Otherwise it's:
Pass the exams- 14 for an ATPL having done approved Ground school ( cause you don't have an ATPL) either fulltime or distance learning ( it's 9 + 7 for CPL/IR so it better to do ATPL).
Flying wise it's hours as required to meet the standard for the CPL and a MINIMUM of 15 hours for the I/R.
It's in LASORs if your want the reference.
W1