Looking into it further I found, via Google, that there was a type of flooring called the Fox & Barrett system that used light weight breeze concrete as filler between joists. It was in use during that time period and may be what Ford was referring to. One reference (PDF) is here:
Originally Posted by Araucaria
George - could be..... but it wouldn't fit the sense very well:
"She sprang off the bench; she clenched her nails into her palms; she stamped her thin-soled shoes into the coke-brize floor that was singularly unresilient."
[in this passage Valentine is sitting "on a varnished pitch-pine bench that had black iron-clamped legs against the plaster wall, non-conformistically distempered in torpedo grey"]
"Of course, our legislators with the stewed-pear brains running about the ignoble corridors with cokebrize floors and mahogany doors…might be impressed."
"The cook-house was like a cathedral's nave, aisles being divided off by the pipes of stoves. The floor was of coke-brize shining under french polish and turpentine."
I'd accept what we called breeze (as in breeze blocks) for a running track surface, or a park pathway, but these scenes are set indoors, in a girls public school in, presumably, Whitehall and in an army camp. But if "cokebrize" is what it says in the original text, it's what it says. Maybe Ford was himself unaware of what the stuff was?
Anyway, thanks again!