You can forget about doing the IR(R) revalidation, as the IPC allows you to then go to the CAA and pay them for issuing an IR(R). They will issue an IR(R) based on passing a third party foreign IR skills test, or proficiency check. It doesn't work the other way round, so you can't do an IR(R) revalidation with an EASA FE, then get the same rights as having done an IPC.
Completing a IPC then applying to the CAA on that basis does not necessarily get you a IMC rating. Rather than renew/revalidate a IMC rating, the CAA normally issue the pilot with an exemption under ANO Article 242 from the provisions of Article 68(1) in respect of the IMC rating if you hold a current IPC. The CAA charge for the issue of this exemption.
Reference for issue, revalidation or renewal on the basis of a current ICAO IR can be found at CAP 804, Section 5, Part E, page 5. However, as a current FE and CFI-I, there is no need for applicants to go through that process or pay anything to the CAA for IMC/IR(R) revalidation since a UK-issued EASA Flight Examiner can sign the Certificate of Revalidation upon completion of the test.
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