Thanks, Mark - this is interesting. The dates, geography and given names of the Quaker Clarks I have found all seem to match up, but they would have had to have relinquished their Quakerism in a generation (sometime between 1737 and 1785) if they're indeed my ancestors. My supposition is that there was a tendency to dissent in the family and that they may have adopted Methodism when they moved to work in a place where there were no Quakers or where Quakerism was frowned upon. I'm just not sure how common such a movement might have been. Thanks again.
Hello Bill
People joined John Wesley (who toured & preached at numerous places), the Wesleyans and Methodists from probably virtually all of the numerous English Dissenting and Nonconformist Sects, besides C of E, Quakers and Catholics, from mid to late 1700s and onward.
Unfortunately with a popular name like Clark, you could have a number of the same surname practising several Sects in the same town and might not be related to your Clark. I have this with my Richardsons.
Wills, surviving Deeds, Manor / Land Owner, Directories, Tax, Parish, Charity, etc and any other surviving records you can find in Archives (many uncatalogued) might reveal people, seemingly missing Baptism / Birth records.
With the exception of church officials who tended to sign adjacent Marriage Register entries/pages, I'm finding many of those present at Marriages and sometimes present at Death as witnesses were nearly always related (even distantly sometimes). Everything must be seen besides the UK Census.
Many Wesleyan supplementary records survive at Archives throughout England. Some moved about a lot too, so assumptions can be dangerous or leave us with doubt.
Mark