Cant see that family at all in 1851 
Neither can I

While looking I found this chap in 1881
John Cortnage 60 Laborer (Farm) born Bepan Sussex living in Headley
RG11/1248/53 Pg15
But can't see him on any other census except possibly in Harting in 41 HO107/1101/4/18 Pg3
With William 50 and Mary 18
As for Bepan/Bepon can only assume this is Bepton

I can check the Bepton registers for you tomorrow, Anna
Jan

Ah there is a baptism on the IGI
John Cortenage baptised Bepton 12 Sep 1819 parents Henry and Charlotte
nothing for Charles or Henry born c1805 though

Will still have a look at the original Bepton registers