At the moment, you'll need 50 hours PIC IFR to do the conversion without a formal course plus it's not a renewal that's required, it's an initial IR Skill Test. Have a look at Appendix 6 to Part-FCL (CAP 804, Section 4, Part L, page 37).
There is due to be a change (no firm date yet) where you will be able convert a current ICAO IR to EASA IR by completing training as required plus a IR Proficiency Check with an EASA examiner as/when the BASA agreement is implemented.
When you say "50 hours PIC IFR" do you mean PIC on flights conducted under instrument flight rules, or 50 hours actual IMC?