You still need to comply with The Local Govt Act 1972 Schedule 12 (2) Three clear days at least before a meeting of a parish council—
(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;
The The Openness of Local Government Bodies Regulations 2014 (S.I. 2014/...) also says
Notice of the meeting specifying the business to be discussed must be placed in a central conspicuous place within the parish or area at least 3 clear days before the meeting. These councils are also encouraged to place copies of the agenda, meeting papers and notice of meetings at offices and on their website, if they have these facilities.
So the website alone is not satifactory, but it might not be necessary to use all 6 boards.