Reader Jan points to this picture of a Royal Enfield dealer in High Street in Brandon, Suffolk, for sale in ebay. It looks from the early part of the 20th Century.
He also helped me identify where it was. Today, it appears that the dealership was replaced with a more modern building. My guess is that it was where "BETFRED, the bonus king" currently is. For reference, look at the second chimney in the left, the one with five stovepipes coming out of it. Also, the building on the right with the phone booth in front of it, is still the Post Office, it is just that the bottom front has been renovated (the top is still as it was). The two buildings to the left of the post office on the right hand side also appear from the period.