Hi Elizabeth,
I've dug a bit further back and found that the most likely parents of John Clegg b 1803 Birstall, were Christopher Clegg and Martha Wood (married 1799 Birstall) and that Christopher Clegg was probably b 1775 Birstall, son of Jonathan Clegg. From the IGI and the 1841 census, looking at the relatives of these Cleggs who were living locally in Adwalton, Birstall, I think you're right in saying that these are "Yorkshire Cleggs".
In the past, when we've been searching through the censuses for our Manx Cleggs on the mainland, these Pennine Cleggs (east Lancs and west Yorks) have made the task a bit like looking for a needle in a haystack.
Jean C