Having a single brand at all your locations will definitely help people recognise you and avoid conusion - especially if you use your brand without any variations on signage at your location.
With the branch number, I'd say do what is right for the customer. Does the customer care about the branch number, for example because it's on their collection notiification? If not, drop it as it's not useful to them and may even lead to confusion. If they do, keep it.
With the city name I'd say the same thing. If yor store signage calls your branch "Widgets R Us London" then having the listing name and the store name match exactly will reassure people they've found the right place. If your signage and other collateral says "Widgets R Us" then drop it. Even if there are multiple locations in one town their addresses are displayed in the search results so there should be no confusion. Have a look at how supermarkets in major cities do it (I'm in the UK so I've just checked Sainsbury in London while writing this) and you'll see that even when they have several branches close together they don't put their locations in the name as the address and the location of the pin on the map is enough to guide people.
Some people wonder about the beneits of including the city name as it might help them appear higher in the local results. From what I've seen including the location in your listing name has very little impact. Your location relative to the point being searched for and the reviews you've received are much more powerful factors. So moving toward a completely coherent brand shouldn't have any negagtive impact on your branding.