Anne, what do you estimate Hugh's birth year to be? When did he marry Isabella? What his mother Barbara's maiden name from his certificates and father John's occupation?
From the names you give for their children, this 1901 census entry would fit - which is what is confusing me re possible ages for Hugh!
Hugh Clifford 34, checkweigher b. Newarthill, Lanarkshire
Isabella Clifford 32 b. Ireland
William Clifford 12
Samuel Clifford 10
Annie Clifford 8
James Clifford 6
Hugh Clifford 4
John Clifford 22, boarder, Coal Miner Hewer b. Carfin, Lanarkshire
Address: Motherwell Rd 4 Benburl Cott, Holytown