Schedule 12 part 10 of the Local Govt Act 1972 provides some pointers but is not specific. But it does say that for an extraordinary meeting, the Councillor (s) calling it provide the agenda as below. If councillors can define the agenda for extraordinary meetings, it would be difficult to argue they can't for regular ones.
"a)notice of the time and place of the intended meeting shall be fixed in some conspicuous place in the parish and, where the meeting is called by members of the council, the notice shall be signed by those members and shall specify the business proposed to be transacted at the meeting; "
But for a "regular meeting" recurring items could be defined by Standing orders, resolutions or policies. However, the Act does not confer the right of the proper officer to decide what other items can be dicussed or not discussed. If that right were to be denied for any reason, lawful or otherwise, 2 Councillors could simply call an extraordinary meeting to have it discussed. That might fail if such a meeting was not quorate though.
" a summons to attend the meeting, specifying the business proposed to be transacted at the meeting and certified by the proper officer of the council, shall be sent to every member of the council by an appropriate method"