If anyone is interested I've managed to find some of the information I was looking for. Harry Capp was married and Buried in Uxbridge in Hillingdon, Middlesex. His wife's name was Hannah Ward and they married in 1803. He died in 1838, which puts his birth year in approx 1775. I still haven't got anything on his birth.

If anyone has any information about any Capp's or Ward's living in or around Uxbridge in Hillingdon in the late 18th Century, I would love to hear from you.