Even if those generations were farm labourers and didn't leave wills, John (and his wife and/or children) could be mentioned in a parent or grandparent's will. Early generations often owned crofts or land, but inherited land went by law to the eldest son (or eldest daughter if no sons) so that younger sons became miners, weavers, or ag labs, etc. - So there might be a piece of land you can go and stand on if you find his parents/grandparents!

I took a scatter gun approach when I was in the same situation, and checked all wills of the same surname in the parish, starting with most likely forenames/dates, until I finally found my ones.
Some possible parents' names were:
John SAYLE & Eliner CORMODE
John SAYLE & Margt COWLE
Thomas SAYLE & Leonora KEWISH

[Wills from Brian Lawson's index]:
SAYLE, John 1799-1 Bri E d 0106406

This is a decree which should name all his children, and who are often underage (often the reason for having a decree / admin). If so, next of kin supervisors will be named, and these often sort out the whole family. Well worth a look!
Also:
SAYLE, John 1806 Bri A 83 0106235
SAYLE, John 1812 Bri E 2 0106415
SAYLE, Lenora 1808 Mau E 1 0106411
SAYLE, Margaret 1818 Bri A 52 0106241
SAYLE, Thomas 1862 Bri A 70 0106264

If you try these, and also the Bride register films, you could get lucky. Well worth a trip to the FHC, and you can order several films at a time. I've looked at Scottish registers and these IoM ones are 10 times clearer.

Sue