Hi Ben, If you need to go forward from your Hugh Cummings and Rebecca Hannah you will need to view their deaths on the GROS official Scotland site. http://www.scotlandspeople.gov.uk/
This is a pay per view, cost 7 sterling pounds for 30 credits. You can do a wide search for Hugh Cummings death (and I feel there would be many) so try to limit you search following the last date you have found him on a census record and you will be aware of his approx date of birth as well as the fact that he was a farmer living in South Ayrshire.
You can view the image and it will cost you 5 credits and 1 credit for the search for Hugh. In the day families lived and died within the same areas so try that first. The other suggestion for you is to access FreeCen http://www.freecen.org.uk/
This being a wonderful resource for the UK. All volunteered transcribers with BMD Registrations and census although not all parishes totally transcribed. I did find Rebecca with her family but Hugh is elusive on the 41. The beauty of FreeCen is that you can check neighbours on either side or down the entire area. Families often lived very close to each other.
The other resource that you can use the Ayrshire Archives site,
The site will be divided into North, South and East Ayrshire, Everyone is always happy to give you help and suggestions to advance your search.