All I know about the British peerage, I learned from Masterpiece Theatre. Lady Marjorie was called that because her father had a title; her husband, as a tag-along, was know initially as Mr. Richard, being only Lady Marjorie’s husband and not yet banged on the shoulder by the King.
After Lady M went down w. the Titanic, acc’ding to Wickipedia, Richard Bellamy ” was elevated to the House of Lords as Viscount Bellamy of Haversham in the New Year’s Honours List of 1917.”
For more confusion, check out Louis Mountbatten, 1st Earl Mountbatten of Burma. He was informally known as Lord Louis or Lord Louis Mountbatten and had both a viscountcy and an earldom. His brother George, was the 2nd Marquess of Milford Haven..
Peerage
And there is George Gordon, known as Lord Byron, among other things.
That should clear everything up, I hope.