I think its important to just remember what you are filling in a cert for. Its to provide proof that nessesary tests have been carried out and to satisfy what work you have done has not impaired the integrity of the installation, with this in mind it may help in your choice of cert to use and what information is required to be included next time. Normally any circuit or part circuit supplied after the point you are altering should normally be included. In your instance I would more likely do the same as Tony and just use a MWC as it would include polarity, earthing blah, blah. But be aware you are saying the existing installation is ok if you don't include/exclude anything so make sure it states that you have not fully tested individule circuits as who would be to blame if any one of those were reversed polarity, no earth etc, Just cover yourself fella.
It would not cost much more time just to do a quick loop and martindale or the likes to random places or the next sparks along the way will wipe egg on your chin or worse. Just a thought !