Yes, the Genuki website states that the Belgravia Sub-District, within St George's Hanover Square is missing. You might get somewhere with a Post Office Directory for 1861, although it would only give you Joseph. I had a look at Leicester's collection but the 1861 Directory isn't included:
http://specialcollections.le.ac.uk/digital/collection/p16445coll4 London Met Archives may hold it.
Richard Tull and his family are at 14 Stockbridge Terrace in 1841 HO107/0732/F? (the transcript has the name as Full and the house number as 13 - took me ages to find).
Mary Ann's brother John married Louisa Basing at Newbury, and can be found in 1861 at 4 Henry's Place Westminster, right by Eliots Brewery where he worked. RG9/0054/F? [Pages 120-121]. In 1871 they are visiting his uncle Henry Tull at Southbridge, Streatley Berks. RG10/1275/F? There are errors in both transcriptions. Alfred Henry Tull, her other brother, is a Professor and teacher of music in Reading in 1851 - Rose Cottage HO107/1692/F? but a licensed victualler in 1861 at the Rising Sun. RG9/0029/F? Louisa seems to have lived with Mary Ann after Richard died, which suggests the possibility she was Mary Ann's daughter, not Richard and Ann's. Louisa died young, 24 June 1872 will proved 1873.
https://probatesearch.service.gov.uk/#wills
