In this case, the Ibid, pp40 at the end of Footnote 7 is sending you back to the citation in Footnote 5, which is an article about postal rates by Richard Breckon, on pages 39-40 of that issue of the journal.
I am finding that hard to follow, I'll re read again.
Is it then correct? or should it be op.cit. ?
or, should footnote 5 have "Breckon" included?
(I am not the sharpest knife in the drawer)
Update: I think I have it