Another image of mine that appears to be on the verge of a complete identification.
The bike was identified as an early 4hp (550cc) Triumph Model H motorcycle. But I’ve just had a Flickr contact do some great detective work based on the name on the shop behind, and there’s a very strong feeling that this must be Pease Street and Anlaby Road in Hull. Certainly the architectural details around the doors and windows are a very strong match with ones that can be seen in photos at http://www.anlabyroad.com/South/pease/pease-street-photos.html
The final unknown is therefore the date. I’m thinking 1920s, but can anyone suggest anything more precise?