Hi there,
I haven't exactly found David,but I might have the rest of his family 

Are you sure about his age? If these are his parents they seem a little young!
Dad is a farmer of 120 acres.
They are living at Tollgate House,Courtland Farm,Brompton Ralph.
RG9/1605 folio 86 page 3
Anna Sellick abt 1856  Brompton Ralph,  Daughter    
Elizabeth Sellick abt 1818  Rose Ash, Devon,  Wife      
Elizabeth Sellick abt 1853  Brompton Ralph,  Daughter    
Florence Sellick abt 1860  Brompton Ralph,  Daughter  
James Sellick abt 1852  Brompton Ralph,  Son    
Robert Sellick abt 1812  Brompton Ralph,  Head  
Robert Sellick abt 1858  Brompton Ralph,  Son   
William Spratt abt 1840  Milverton, Somerset,  Servant    
William Bishop abt 1841  Bagborough, Somerset, Servant  
Ann Hooper abt 1845  Brompton Ralph,  Servant  
I also found a Samuel Sellick born 1843 in Brompton Ralph, living with the Bodley family in Marylebone London,working as an apprentice to a Grocer.
But where is David  

Hope this helps,
Regards
Carol