I have ancestors from Hull. I have found a marriage certificate that I think is theirs but that places their marriage in Leeds. How likely is it that they would travel all the way to Leeds to get married? Bear in mind that the woman was born in Leeds but had not been living there prior to her marriage.
Population Studies from Parish Registers, a selection of readings from Local Population Studies, edited by Michael Drake (Local Population Studies, 1982, ISBN 0 9503951 7 X) contains a number of papers concerning this problem.
Bessie Maltby found that in Easingwold (NRY) in the period from 1644-1812 3% of partners were from a parish over 20 miles away.
In Colyton (DEV) E A Wrigley reports that something like 20% of wives were living more than 10 miles from their parish of birth, based on an anlysis of the baptism registers for 1765-77 and the 1851 census.
A third study by Jeremy Millard was of 6 parishes centred on Stony Stratford (BKM). He found that the distance travelled for marriage depended on date and transport links (eg, turnpike roads, canals and railways). He carried out a detailed statistical analysis with the following results:
Extra-parochial marriage distance (km) mean upper quartile 1754-1793 29.8 34.2 1794-1833 23.9 31.5 1834-1873 34.7 60.3 1874-1913 49.0 80.9
So, the 50 miles (80 km) from Leeds to Hull is on the high side but not out of the question, particularly as there was a direct railway line from Hull to Leeds via Selby by 1840 (see http://www.railmaponline.com/index.php and https://en.wikipedia.org/wiki/Hull_and_Selby_Railway).
The other thing to bear in mind is that many young people took up apprenticeships or worked considerable distances from home, even in the 18thC. Possibly she returned to her parents home for the marriage.
Do away with the perception that our ancestors didn't travel far. Especially by the nineteenth century there were several forms of transportation. Horse and carriage would of course be most common, but with the advent of the railways and expansion of roads, transportation over longer distances became easier and more accessible. People also walked long distances.
I'm reminded of this gem I once came across in the Notts Guardian for 9 Aug 1849:
Leeds and Hull are just 60 miles apart. 90 year-old Nanny Fowke walked well over 100 miles to London. Certainly not everyone would have walked such distances, but keep an open mind that our ancestors may have been more mobile than we tend to think, even if they were not a person of means.
Regarding travel for a marriage ceremony, you should establish how long they may have been in Leeds. If they married by banns then one of them had to have "resided" in the parish of Leeds for at least three weeks. If they obtained a marriage license, they may have only been in Leeds for a very short time. In such case other records such as a marriage bond or allegation may give interesting insight into why they married in Leeds. Looking at my own family tree it is not uncommon for my ancestors to travel to another city to get married. In some cases, there were employment opportunities in that city which may have been one draw, but in other cases my ancestors seemed to go right back home after they were married. It does make me wonder whether they travelled to get married more privately and away from prying family eyes, but that is nothing more than speculation.
In your case you mention that the bride was originally from Leeds, in which case I think it is not at all surprising that they travelled back there to get married. Even if she had been living elsewhere just before marriage, she may have considered Leeds her home and wanted to be married where she had family ties.