My 3-greats grandfather was a John Dinan, born in Ireland, I am not sure where, supposedly around 1815. There's an interesting map of the Dinan surname, ca. 1850, at: http://www.irishtimes.com/ancestor/surname/index.cfm?fuseact...
This John Dinan came to NYC from Liverpool aboard the ship H.H. Boody, arriving 13 July 1850. He's the only Dinan on that pasenger list, but it's possible his cousin had a different surname.
Do you think wife Ann may have died prior to 1850? In NYC, this John Dinan married one Mary Brennan and prior to 1860 moved to New Castle, Westchester, NY. Their children were born in 1854, 1856, 1858, and 1863. (I'm descended from Mary Ann, born 1858.) In the 1860 census, he's in New Castle. It's possible that he served in the Civil War, though he's in the 1870 census, so this John Dinan didn't die in the war.
What's the evidence that your John Dinan moved to England before ~ 1835? That's very interesting. And the evidence that he died in the Civil War? These may be two separate people.