I never quite got top grips with these 'British Edition' reprints myself. Your Flash is a T&P, but has no T&P cover logo, and the reprints of ACG titles were by Arnold but did carry a T&P logo:
This from a GCD entry:
Notes Later issues at least up till #18 have Arnold Book Company as the indicia publisher, but a cover brand of "TP" (Thorpe & Porter), possibly because Thorpe & Porter distributed the issues for Arnold.
When I plotted T&P stamps on ACGs I tried to match the reprints up, but they are all undated.