Whoppity states:
The privileges of a CRI are clearly written in JAR-FCL 1.375: to instruct licence holders for the issue of a type or class rating for single pilot aeroplanes.
My conversations and emails with the CAA indicate that this paragraph is not as clear as you might like for two reasons. First, it does not specify what TYPE of licence. TV license? NPPL? JAR license? The consensus thus far is that it means "JAR or other ICAO license". That rules out the sub-ICAO NPPL.
The second issue is more tricky. Is a license with no valid ratings still a license? Some of the people I've spoke with at the CAA seem to believe that as soon as the last rating expires on a license, the license itself ceases to be until a rating is re-applied. There are further questions as to whether this happens immediately, or after five years etc, and what happens when the SEP expires but the IMC is still valid.
Until the CAA make up their mind, clearly, on both of these issues, I for one will play safe with the people I train. I owe them that much professionalism.
As regards aerobatics, you're quite right that no formal license is required to teach aeros, however the CAA is very clear that a freshly-minted FI(R) may NOT teach aerobatics. No such restriction is written in my CRI.
As regards instrument training, an FI(R) rating again specifically excludes applied instrument (and night) training, but both restrictions can be lifted from the FI(R) rating
without adding an IRI. However, no such restriction clause appears on my CRI rating.