Just to add for UK pilots there is the option of doing the IRR, after which the IRR privileges can be used to accumulate p1 IFR time (due attention should be given the difference between IFR and FSRI, ie flying under the hood in class G en route with a safety pilot is P1 but not IFR, but any practice IF approaches could be logged p1 IFR).So yes for UK PPL holders with an IRR you can do IFR hour building, that would allow a IRR holder to accumulate the 40 hours IFR as a requisite for the CB IR. 15 hours from the IRR and potentially the remainder 25 from using the IRR.