You are perfectly correct in your understanding.
My reasoning was was as follows:
1. A parish council has a primary duty to hold an annual meeting + 3 other meetings in each municipal year (LGA 1972 Schedule 12, Para 8)
2. A parish council has an equal primary duty to advertise those meetings at a conspicuous place in the parish (LGA 1972, Schedule 12, Para 10)
3. In everyday language that means notice has to be posted.
4. To post a notice it is reasonable to argue that you need a noticeboard hence I have suggested using the subsidiary Section 111.
Having said all that, I do not fall out with your suggested use of S142,