We have had a look in Haddenham church, just across the county border in Buckinghamshire. As in so many English churches, there were clearly substantial survivals there of medieval glass; destruction by sixteenth century reformers, and Puritan vandalism, undoubtedly happened, but affected quite a small part of England. As far as the South West is concerned, Symonds' diaries, and Milles' notes, indicate how much medieval glass survived (respectively) in the 1640s and the 1740s. The Georgians did have a bit of a passion for plain glass; but my instinct is that most of what has since been lost simply fell victim to decay and lack of interest. Around Oxford, for example, the recusant squire of Milton Manor in the 1760s was able to collect, and insert in the 'Strawberry Hill' chapel which was part of his house, quite a bit of mediaeval glass from local churches ... clearly, they were quite willing to let it go! Perhaps he gave them some lovely plain glass in lieu? An 'Alderman Fletcher', who became interested in such survivals, was able to collect a vast amount of glass, much of it of fine quality, in the 1820s. Some superb panels of the martyrdom of S Thomas left his collection for the windows at the end of Duke Humphrey; the residue he donated to Yarnton church just north of this City, where it can still be enjoyed.
What survived in many churches until the later nineteenth century tended to be gathered together by the church restorers into one or two windows, often consisting of unrelated quarries juxtaposed in patterns. At Haddenham, one window apparently contains a couple of figures of Apostles ... and a considerable amount of writing. The disjecta membra of the Apostles' Creed can easily be discerned.
Thirteen or fourteen years ago, in Brittany (I can't remember where; somewhere near Pontrieux), I came across a perfectly preserved late medieval window showing each of the Apostles with that clause of the Creed which, tradition held, he had contributed. Clearly, just such a window once existed at Haddenham.