Possibility?
D/1930/49/1007/113/3 Maria Todd 31st December 1929 76 Female Belfast
Thanks for this.
OK, I've had a look at that on geni.nidirect.gov.uk. I did my own fairly wide ranging search and found only one Maria Todd kept coming up. I looked also in civilrecords.irishgenealogy.ie but curiously couldn't find a Maria Todd death record there anywhere. Lots of Marys but none seem correct.
Anyway, although the age of 76 seemed wrong (age 50 in 1901 census would suggest age 78 in 1929), I paid for a 'full view' and sure enough, present at death is one Mrs J Cummings. Thanks to 'tonepad's earlier post, we know that her daughter Lavinia married Thomas John Cummings, so that would be Marias daughter. That makes the connection well enough for me. And yet another address!
I saw that the death record of John Alexander Todd showed an address of 51 Lisburn Road not just for him but for others too on that page, which seemed odd. After searching, I discovered that to be the address for the early incarnation of what later became Belfast City Hospital. So he was ill in hospital on the date of the 1901 census, so that's why he wasn't recorded at home on that record.
All very satisfactory.
Thanks to everyone for all the help with this. I've now got much more information than I ever expected.
I'll no doubt be back asking for more help when looking into my maternal family.