An 1872 reference describes Alstone Road as running parallel with the Gloucester Road. This would tend to suggest that the location of the Why Not Inn was to the east of Alstone Road/Lane rather than to the west where the Gloucester Road is roughly on a north-south orientation. There is no reference to the pub in the 1891 licensing records.
Alstone Road is most likely the road which is now called Alstone Croft. A really old way which included what is now Arle Avenue. In my opinion both predate Gloucester Road in that area. Gloucester Road is far too straight and has a touch of purposed design about it.
Gloucester (a son of Alstone Lane)
1870 George Williams
1872 J. Stephens