Thank you to Aditya for the support I have received so far, it appears that I have worked it out now. The series of 'Shift Logs Raised' had the User Namefield as a category and that was why the name was being pulled into the X axis.
This option can be found by clicking on the axis on the graph, then right clicking, going to [Series Property], [Serie Data] and then [Category Field].
Thank you, I hope this helps others in future.