According to John's Service Records from the National Archives, it was noted that he served in the West Indies from April 1819 to April 1826. (I think this is noted because in his pension? they were only allocated half pay). The next positive fact is when John Junior is born in Portugal as Ammanda says. John and Emily therefore could have been married in the West Indies, England, Portugal, France or Belgium - if you can find the marriage Merry, you are an absolute genius.