I opened up Paul Meyendorff's translation of the 'Eccesiastical History and Mystical Contemplation' of St Germanus of Constantinople, On the Divine Liturgy (Crestwood, NY: St Vladimir's Seminary, 1999), and lo and behold, on the first page of the introduction, Meyendorff cites Brightman. He is discussing the influence of St Germanus in Russia and the inclusion of the commentary in various liturgical texts there, and then observes in a footnote, 'These are catalogued in F.E. Brightman, "The Historia Mystagogica and Other Greek Commentaries on the Byzantine Liturgy", Journal of Theological Studies 9 (1908) 248-257;...' (Meyendorff, p. 9).
Meyendorff refers to Brightman again on page 19. Having quoted the Introit Prayer read by the bishop during the third antiphon in the Liturgy of the Catechumens, Meyendorff notes, 'The original Greek text, which appears in the earliest extant euchology, Barberini 336 (ca. 795), can be found in F.E. Brightman, Liturgies Eastern and Western (Oxford: Clarendon Press, 1896) 312.'
(The illustration is a drawing of the exterior of Magdalen College, Oxford, where the anecdote I related about Brightman took place. I still have not found an image of the painting in the C.S. Lewis book I have mentioned, the interior of the Common Room, or of Brightman himself.)