Hi Fred
Very interesting photo, and some great work from China!
Re the name on the marriage certificate being Harry Richard, vs Henry Richard in the 1891 census as manager of the off license - Harry is a well known shortening of Henry.
But as China says, you may well have to invest in the birth certificate, reference as found, to see what turns up. Very likely to be him, and it will give you his mother's name and maiden name too, so you can follow them back and see if the marriage between Henry Richard Wilkinson and Clara J Mostran is the right one.
I think the photo itself may be cut out from another picture, as suggested, perhaps of other boys at the school? If William's father was in trade, and doing reasonably well during William's youth, perhaps he did go to a private school with an Eton-type uniform.
Perhaps something happened to Harry Richard's business - we all need to have another look for him in the 1901, and also in the 1911.
With regard to the photo, what's William got in his left hand - right hand is the dog's lead, in the left?