I know a lot about Hugh and Isabella's children - I have some photos of some of them. I know a little bit about your grandfather too (assuming he is the right man). I think I have some records on him in my family tree mess! I know about Hugh and Isabella's parents and also brothers and sisters too. They lived in the village I still live in now, and if your grandfather is the son of Hugh and Isabella I also know that he lived in this village too. Hugh Snr. was a relatively successful footballer in his younger days.
I have a record for a Hugh Clifford, born abt 1897 who married a Jane Shiels in 1921 in Carfin - he is Hugh and Isabella's son. This would be the Hugh who is your grandfather - I think! Do you know what year he died and where?
I will send you a PM on here with my e-mail address as it will be easier to communicate through e-mail, I think - if you don't mind.