These dates are before the beginning of official registration (1837) so you won;t get certificates for them. You might get baptism records though - have you tried the IGI?
you probably have this already but just in case name; hannah king chr. 21st sept 1828. place; tetbury. parents; john-mary ann king. batch no. CO54862 source call. 0856950 type; film. ext.rec. IGI this is the only christening that appears on the IGI between 1818-1838 for these parents in tetbury.
Logged
cattell,alcester vickers,sulgrave hewish,holborn manley,bethnal green barnes,bassingbourn
there is this one in tetbury name; john king chr; 6th oct 1822. place. tetbury parents thomas-mary anne king. batch CO54862 source call no;0856590 type; film ext.rec. IGI
Logged
cattell,alcester vickers,sulgrave hewish,holborn manley,bethnal green barnes,bassingbourn