Kodak Express

Very friendly, very helpful photography shop. They can do all your camera and imaging needs, it seems, and not in a tiny, cramped little corner shop like some of them are.
They can also do a full range of passport photos, even for non-​British ones. Take in your spec sheet and they can digitally manipulate the photo they take to match whatever you need. They did my Canadian passport photo (quite different, at least now, from the British one) so that it precisely matched the border and face size specs. They did the manipulation and printing in about 20 minutes, and were happy to write the required detail about the location of the shop that took the photos on back.
And they did it all with a smile. Thanks.