I think you need Ancestry for Army Records, not all survive many were lost to bombs and fire etc during WWII.
Given his age and the timing of his marriage begs the question.
What was his occupation on his marriage cert? (Many marry just after leaving Army Service).
If still in the Army he may have served in the Boer War.
Have you got him in any Census.
If you have a photo of him in uniform there may be clues as to his regiment.
The more clues you have the easier it will be to find the correct John Dwyer.
Also this needs to be moved to Armed Forces board, click on report to moderator and someone will move it for you.