I *think* I have finally tracked down E. Downey - or more correctly, Edwin Stanley Downy. From online genealogical records I have established the following:
Edwin Stanley Downy, born 23 Feb 1905 in Camberwell, London.
1911 Census: father was Henry Downy, a printer machine minder living in Chalk Farm, London, his mother was Laura and by 1911 he had 2 brothers and a sister.
1931-32: on London electoral register
1934: married Marie E Constantine in Camberwell
1939 Register: Listed as a Table Glassware Designer, living at 9 Beech Gardens, Gateshead with his wife Marie E Downy (which would possibly tie in with Adam Dodds' memory of a designer called Downy being connected with Sowerby's before WW2).
1946: on London electoral register in Wembley with his wife Marie E Downy
From 1947: on electoral register in Ealing with his wife Marie E Downy
1977: died in Ealing