There were several houseplants in the house, including a begonia and an aloe. Once, having left for Blackpool, Graham forgot to water the plants, and Vera withered away, leaving the begonia to mourn the love of its life. (PROSE: The Secret in Vault 13)
When they first met the recently-regenerated Thirteenth Doctor, and she fell unconscious, they took her to their home. When the Doctor woke up from her nap, she complimented them on their sofa. (TV: The Woman Who Fell to Earth)
Following Grace's death, Graham and Ryan continued to stay there when not travelling with the Thirteenth Doctor. Graham actively chose to travel in the TARDIS, as his house was haunted by memories of his loss, and he needed time to process his grief. (TV: Arachnids in the UK)
Team TARDIS returned to water Graham's houseplants, a few weeks after they had left in Earth time. The begonia finally managed to revenge Vera by betraying Graham and Team TARDIS to the Gardeners. (PROSE: The Secret in Vault 13)
Behind the scenes Edit
In the real world, the Sheffield house which stands in for Graham's house is located at 36 Shrewsbury Road, just outside the entrance to the Park Hill flats. In Arachnids in the UK, Ryan says to Yaz "Wait you live at Park Hill? We're just up there", implying that the house is just up the road; this lends credence to Graham's house being located in the same place within the DWU.
Though it's possible that a real world location doesn't exist in the same geographic space in the Doctor Who universe, such cases are few and far between. Thus, the map at right is probably a good indicator of the DWU location of Graham and Grace's house.