I have always taught that when the FISO states "at your discretion" that you should give your intention
When a FISO states "at your discretion" it is a signal to you that the FISO has no controlling authority and that anything you do is "at your discretion". You do not read this back as it is not an instruction however; you acknowledge, and may well include information relevant to the FISO and any other traffic on the frequency (at your discretion).
The Suppliment contained a number of differences from CAP 413, maybe why its been withdrawn! Have you looked at CAP 797
Flight Information Service Officers Manual?