Sounds very unsatisfactory!
A meeting of a local council that is not preceded by the public posting of the agenda three clear days ahead is not a lawful meeting and cannot lawfully make any decision.
A council cannot lawfully make a decision on a substantive matter that has not been included in the agenda.
All council meetings must be open to the public. It is possible to move a resolution to exclude the public during the meeting, although the general nature of the reason for exclusion must be given and must fall within the legislation e.g. allowing the public to be present would breach an obligation of confidentiality. Members of the public are entitled to be present at a meeting until such a resolution is passed.
Every council decision must be recorded in minutes, which should be signed at the next opportunity. In practice this means either at the meeting or at the next meeting. Electors of the parish have a legal right to inspect all council minutes at reasonable times. Electors who inspect the minutes are entitled to communicate their contents to others if they wish.