Earlier this year I began seriously tracing my family history. I've found the experience strangely therapeutic, often frustrating but always rewarding. I have used mainly online resources and at times reached out to several organisations and individuals to no avail, no one seems to reply. Reluctantly I am asking for help and advice with the following, I say reluctantly as I feel like its 'cheating' but I have reached the 'brickwall'.
I am trying to trace where my Great Grandparents were buried, their details are below:
Margaret (Maggie) Sinclair, nee McGhee born 19 June 1874, died 29th November 1909 (Baptised 28th June 1874 St Patrick's Coatbridge, married 28th November 1890 St Bridget, Baillieston). Death registered Coatbridge her age and mothers maiden name were incorrect on the death register. Her dad was John McGhee (1843-1915) and mother Mary McIntyre (1847-1918).
William Sinclair born 18 September 1869, died 6th January 1939 (baptised 27th October 1869 St Patrick's Coatbridge, married 28th November 1890 St Bridget, Baillieston). Death registered in Old Monkland Western District. His dad was John Sinclair (1835-1921) and mother Jane Kelly (1836-1877).
At the time of their deaths both lived in the Bargeddie area of Coatbridge. All their children were born in this area and all baptised from St Bridget's in Baillieston. They had three children who died in infancy and all three deaths were registered in Coatbridge or Old Monkland district. All three children were buried in the common ground areas of Dalbeth St Peter's. I assumed that both Maggie and William were also buried here however they do not appear on the Dalbeth burial records that appear online at Scotland's People. Is there any way of finding out where they were buried, Old Monkland Cemetery is close by and would be a likely alternative to Dalbeth St Peter's. St Joseph's in Airdire is also an option.
In June I emailed the Scottish Catholic Archive and got an automated out of office reply and then a reply from an archivist saying she was on holiday until 12th July and thus had no access to her records but she would pass my query on to the Dalbeth staff. I heard nothing back so I emailed again on July 19th but again have had no reply. Can anyone tell me if this is typical? As I am a carer I don't really get time to visit places but last week I had a free morning and decided to set off to Dalbeth (promising my wife who is the driver that there is a Range store nearby), there the ground staff said they only keep ten years worth of record on site.

I also have a burial record for William's father John Sinclair who was buried in St Peter's Dalbeth on 8th November 1921 aged 86, he was buried in one of the three common ground areas. However unlike any of the other records I got from Scotland's People the record has the number 320 written after his place of death, on the same page eleven more people have the number 320 while others have 317, 318, 319 etc. Does anyone know the significance of these numbers, might they help identify which area of Common Ground John is buried in?
Any help or advice on my next steps would be fantastic and greatly appreciated,
Dean