Hi
According to the Streetmap website Alpha Road is still there but the map gives no further clues that I can see.
If you go to historicaldirectories.org
click on Kelly's Directory of Essex 1894
and search for McMullin you get on page 95
'McMullin Henry water bailiff to Mrs Heathcote, The Fishery'
If you search the census for 'Heathcote' in Chingford that may pinpoint the fishery.
I looked further at the same directory and read that Mrs Heathcote was a major land owner in Chingford and lived at Friday Hill in Chingford.
I wonder if the fishery was Connaught Waters - still a fishery apparently.