Section 91 of the LGA 1972 states:-
"Where there are so many vacancies in the office of parish or community councillor that the parish or community council are unable to act, the district council [or Welsh principal council] may by order appoint persons to fill all or any of the vacancies until other councillors are elected and take up office."
In the absence of any other reference, I presume this arrangement might apply to parish meetings, although the legislation gives the district council a power, not a duty, to intervene, so in the case of a parish meeting, they might decide not to. Without a functioning parish meeting, no expenditure is permitted and no precept can be set for future years.