I am looking for the marriage record of George Dixon and Harriet Colgate that took place in about 1848 in either Middlesex or Kent. I'm not sure what religion they were but in the 1851 census their civil parish is St Marylebone and Ecclesiastical parish is Christchurch. (I'm not sure what those terms mean exactly)
George was born in Crayford, Kent, in about 1819 and Harriet Colgate was born in Eynsford, Kent on Nov 9th, 1827 to Charles Colgate and Lydia Millbourne. The birthdate of their first child, George W, was Dec 21st, 1849. They had two more children, Alfred and William, and then the father George died in about 1857.
I have tried every combination of wildcard characters and spellings of Dixon and Colgate, and using only first names and only last names, and combinations of the two. I've used ancestry, familysearch, findmypast, and probably every other genealogy website out there at some point and have had absolutely no luck whatsoever. I know the the Colgate surname has some deep roots in Kent so I'm surprised I haven't been able to find anything.
Does anyone have any suggestions on where to look next for this? I'm from the US so I'm not that familiar with how UK records are indexed, organized, or even specifically which ones exist, so maybe I'm just missing something.