Well, what a lot has gone on while I've been offline! Thanks, everyone, for your efforts so far. The addresses actually came from the 1894 Directory of Northumberland, so I know who ran the shops in that year (Gadget and Jora, you may remember a certain Italian lady?). 1891, though, is a bit on the crucial side for events in my family. Knowing who was at those addresses then tells me an awful lot (or, as it may turn out, knowing who was NOT at those addresses).
Anyway, knowing now that the Walkergate premises was a pawnbrokers/drapers transfers attention to the High Street/Marygate address - and if that one turns out to be a confectioner/ice cream maker, it's Bingo time. If it doesn't, I have a fair bit of rethinking to do

Mike