When I first started my family history, I used to ignore individuals whose names weren't spelled exactly like my other ancestors. I have a family of Dickins, and so tended to look for that spelling and more or less ignored the Dickens, Dickons, Diggens, Dyckins etc.
Gradually, as I gained experience, I realized that before the 19th century, people weren't so bothered by spelling, and might spell their names in a variety of ways. For census returns up until 1911, you are very much reliant on the spelling and care of the enumerators (and nowadays, the transcribers for family history sites).
I have made a couple of big mistakes regarding spelling of names. I found my grandmother's family in a census but rejected it because the child's name was spelled Hanoria, and my grandmother's name was Honora. It turned out to be the right entry.
I also rejected a marriage in the late 1800s because the name given was Clark instead of Clarke. That, too, turned out to be the right entry, and the only time my great grandfather seems to have used Clark instead of Clarke.
We think of surnames as fixed things, things that travel with us through life, but that wasn't true for a very long time. In Anglo-Saxon England, there was not a great need for surnames. People generally think that's because no-one travelled, but that isn't true. The reason that there was little need for surnames was that parents would give children a unique name, something that no-one else was known by. Sometimes these would be attributes that they hoped for their children and sometimes an attribute they already had.
When the Normans conquered England, they brought with them a tradition for using Biblical names for their children, and a tradition of using nicknames to describe people. William the Conqueror would be an example... though he was also known as William the Bastard.
Strangely, the people of England quickly abandoned their traditional names in favour of the Biblical names which were liked by the Normans, and thus there might suddenly be four Johns and ten Henrys in a small village... some sort of surname to distinguish who you were talking about was necessary.
In the beginning, a man might have a lot of different surnames. He might be called William the Red, because of his Red hair... or William the Smith because of his profession, or William John's son, because of his family. He might move house and be called William Rivers because he lived near the River, or William Cooper because he had changed profession.
It took a while for names to settle into families too. Sometimes two brothers wold have entirely different surnames because they had different professions, or one identified himself as John's son, while another was a miller.
For most of England, the surname seems to be fairly fixed by the 16th and 17th centuries, but this isn't true all over the country. Cornwall and Devon seem to have been still using flexible names by the end of the 18th, beginning of the 19th century. Wales seems to have used the father's christian name in succession, for many years.
It is always something that needs to be considered, whether an ancestor may have changed his surname in the course of his life... and whether he may have changed the spelling for some reason. My Dickins ancestors seem to have adopted Dickens in the course of the 19th century, maybe to link themselves to Charles Dickens, or maybe because people had begun to assume that was how the name was spelled.