Am I correct in thinking that for a BCPL (A) with AFI (restricted) rating who would like to instruct in 3-axis microlights
Legally yes however, as the microlight syllabus is considerably different from the SEP syllabus I would advise you to obtain some guidance from those who teach regularly on microlights, your students would most likely be tested by a microlight examiner. You should also have a reasonable level of microlight experience, 5 hours is recommended for different types but I suggest a little more would be sensible.
"Differences Training" was originally listed in JAR-FCL but it disappeared! It has never been in the ANO except for the SSEA Class on a NPPL!