I too have checked the 1851, if this is the Daniel Dimont to Grace
Trevett 1795 they would be in their 70's if still alive. I will try to check 1841. Could not find their son Daniel( 1796 )but plenty of David's but not born 1803. Do you have any more sons names and ages as I will check them to see if they are living with them. Only one in Symondsbury in 1851 is James Dumant aged 15.