Good Morning
I've pondered this over night and done a little more digging.
Have you considered earlier censuses ,pre 1841?
Chobham censuses have survived 1801,1811 and 1831 which may help for the Bartletts.
Apparently 1801 has everyone named.
Headley Hants apparently has a population study 1820-1830 (It has no date but was probably done for the 1821 ) at Surrey Record Office in the Guildford Moniment ? Room.
Usually they is some kind of box to tick for ages male ,ages female in 10 year gaps which could be worth a look.
The how about militia lists of young men eligible to be called up for military service? Not the ones who actually joined up to fight Napoleon but who could be called up. Every man 15 to 50 in theory should be on the list.Have they survived for Surrey ?
And tithe maps for East Clandon and Headley does Stephen Ellis senior appear on any of them?
And this is just a wild card but there is this couple
Stephen Eyles and Elizabeth Worsefield married 7.11.1766 at Elstead St James
He is from Farnham and she is of this parish
Witness Richard Edglen and Thomas Collyer
They go on to have the following children -James 3.4.1769-6.4.1769 ,Mary 10.2.1770 ,Sarah 6.9.1771-23.3.1845 ?,Elizabeth 1.6.1773,Charles 11.4.1775,William 21.6.1777 Elstead,Thomas 25.7.1779 -28.11.1793 ,James 16.3.1781-29.3.1829 ,Ann 25.4.1783 ,and Hannah 27 .3.1785.
Mostly at Godalming
Stephen Eyles was buried at Godalming 21 Oct 1813 Born 1738.They is a Death Duty record which may be enlightening for 1815.His Will says he is a wheelwright and leaves everything to his wife Elizabeth. Elizabeth his widow in 1828 mentions daughter Sarah and then residue to rest of my children.Again her Death Duty record may be more help.
Could there be an older son Stephen born c 1768? It's just that there is a Charles and a Hannah like your family and Godalming seems a strange coincidence.
Just a thought
Ciderdrinker