In the first of the following links is a table of what I believe to be the last 78's issued by each of the major UK labels.
In the second of the following links is a table of what I believe to be the last UK records to be issued only as 78's.
These are based on data in the New Records magazine and the Gramophone popular record catalogue. Usually these two sources agree but not always. Also the Title and Artists sections of the Gramophone catalogue sometimes give different information about whether a 78 version was issued.
The Tables refers to links and these are listed below the links to the tables.