FI Renewal
You are partly correct in the format of the instructor test. The 45 minute talk does not necessarily have to be on the subject of the airborne exercies. For the flight test itself you can expect to have to give a pre-flight brief on the main exercise followed by the flight which will consist of the exercise you have briefed plus other manoeuvres. Exactly what you will have to do depends to a certain extent on your instructor rating, for example if you are an IRI you will be expected and briefed to do some airborne instruction of applied insrtument flying as werll as the main exercise. At the end of the flight you will be assessed on the debrief you give your "student" and to finish the day off there will be an hour or so of questions to test your overall knowledge. I am not sure off the top of my head, but I think that if you log onto the CAA's website you should be able to download a form known as the F682. It is the form that the FIE uses for his own records and on it you will see exactly what he will be testing you on, including the oral examination subjects.
Hope this helps and all the best with the renewal.
M1.1