Thanks, David - it's starting to come together.
And thanks, John - the Wesleyan William must be the son of Thomas and Christian bap 1769, who married Mary Warren of Haynes and raised his family in Wilstead.
So at least some of the Armstrong family WERE Methodists, then. Now, if there were no Methodist chapel in a village or town, would a travelling Methodist minister be allowed to use the parish church to do baptisms?
Some results of my labours:
The NBI has 13 John Armstrong burials in Bedfordshire - assuming that all parishes have been included by Bedfordshire FHS on the database they have provided to Family History Online. The list looks pretty complete to me, but I am not a Beds expert!
I have identified all of them - or dismissed them because they were buried before 1760.
There is only one burial that could be the John baptised 1762 in Wilstead, and that is:
John ARMSTRONG Date 14 Nov 1826 Aged 66 Place Ravensden Description All Saints Denomination Anglican County code BDF.
It is, of course, possible that John bap 1762 in Wilstead could have moved out of county. But if he did not, then the Wilstead-Ravensden link is looking possible.