From what I have been told:
If your CIR has been expired for less than 12 months, then a standard renewal test is all that is required. Only one approach needs to be done in an a/c, whilst the rest can be done in an approved sim.
If your CIR has been expired for more than 12 months (ie. 2 years since your initial issue or last renewal), You do not have to re-do your entire initial issue training. However, the renewal test required to be able to exercise the privileges of your CIR is the equivelent of an initial issue test and has to be completed entirely in an a/c.
ML