Surely the 'non-grammars' in a selective (grammar) area are Secondary Moderns, not Comprehensives?

YES THEY ARE in Lincolnshire which still operates the tripartite secondary system.
Not sure about Kent and bucks.

In all other areas, the grammars are anachronisms

en.wikipedia.org/wiki/File:Grammar_school_ballots_in_England.png

No, they're not. My DC chose not to take the 11+ and so go to a comprehensive that really does take pupils of all abilities. It has pupils that go to Oxbridge and pupils with quite severe SN.

My DC wanted to go there and not to grammar. Part of the reason was because the grammar schools in our area are single sex which they didn't want and neither did I, having attended a single sex school myself. 2 out of the three are in the top sets for all setted subjects at secondary school now (not all subjects are setted). Children can move up and down between sets which seems to work very well. My DD has just chosen her options for GCSE and the top sets are being told to make sure that they take a language so that they get the English bac (even though it's not an actual exam).

The most able at my DC school are told to aim as high as any grammar school child.

No, because you don't fail the 11+ to go there.

We have access to three grammars but at a bus trip away. Many very able children go to our town comprehensive. Last year 10% of the children got 8+ A-A* That is not a secondary modern cohort.

There are a lot of parents who still believe that able and motivated children will thrive where ever they go. If those parents are right, the children will also have the advantage of attending a school with no social selection and saving a lot of travel and possibly a lot of tutoring in year 5 and 6). These children are not secondary modern learners.

No, they're not, because even in selective areas the 11-plus isn't compulsory. Many parents elect to send their children straight to the comprehensives to avoid their children going through the stress of a selective exam.