It seems like one hell of a coincidence. I can't believe that. Perhaps there was some family connection between the Hull and London Keelings? It seems strange Elizabeth is in London at all but to get married at the same, relatively obscure, small parish church seems too unlikely to happen by chance. The records are on FindMyPast so I can't give a direct link.
The General Magazine of Arts and Sciences: A Chronological Memoir of Occurrences
Sept. 1. Mr. Wm. Keeling, of Thames-street, to Miss Philby.
This suggests the couple were fairly affluent.
First name(s) William
Last name Keeling
Marriage year 1756
Spouse's first name(s) Ann
Spouse's last name Philby
Place St Peter Cornhill
County London
Country England
Source Boyd's marriage index, 1538-1850
Record set England, Boyd's Marriage Indexes, 1538-1850
Category Birth, Marriage, Death & Parish Records
Subcategory Parish Marriages
Collections from England, Great Britain
First name(s) John Benjamin
Last name Frentzel
Marriage year 1778
Spouse's first name(s) Elizabeth
Spouse's last name Keeling
Place St Peter Cornhill
County London
Country England
Source Boyd's marriage index, 1538-1850
Record set England, Boyd's Marriage Indexes, 1538-1850
Category Birth, Marriage, Death & Parish Records
Subcategory Parish Marriages
Collections from England, Great Britain