British Smilers: Custom Postage in the UK
Custom postage in the UK goes by the name of Smilers. The program there is similar to those in other countries. As in Canada, people can mail in images if they wish to, and here too they are advised to copy originals before sending anything in, just for security.
They recommend a vertical shot to fit their postage size, and recommend that it be sharp and clear.
Their regulations are similar to American ones in requiring the postage image to be in good taste and non-controversial, and similar to Canadian ones in requiring you to have permission from anyone before you use a photo that includes them on a custom postage stamp.
As this example shows, their stamps are quite different from American and Canadian ones in that they are composed of two parts. For this personalized stamp, I uploaded the image of the greenery and then chose what to put on the right side from about a dozen options.
In the UK, Smilers may not show a business logo or slogan but businesses can combine their own images next to a first class Royal Mail stamp.
Also offered are a selection of generic Smilers, with popular images on them.