Thanks John. Well spotted!
It all seems to fit. I have also since found out that by 1946 he was still trading as Arthur Day and Son(s?) no longer as piano manufacturers, but now in the business of Radios. By then Arthur would have been about 73 so could well have handed the business over to his son, who clearly decided he knew best! The last recorded entry I have is from 1953, when the business was still trading as Arthur Day and Son, still doing radios, and still at the same address at 15-17 Upper George Street. But what happened to the shop? Is it still there? Who was his son?
Thanks once again, John. Much appreciated.
Steve