After some different approaches to this I created a simple .py script that updates the table with all the fields I need. See below.
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import arcpy
from arcpy import env
env.workspace = r"C:\X\X.gdb"
for PopSummary in arcpy.ListTables("*"):
try:
arcpy.AlterField_management(PopSummary, "Sum_Pop_T11", "", "TotalPop")
arcpy.AlterField_management(PopSummary, "Sum_Pop_014T11", "", "Pop_014")
arcpy.AlterField_management(PopSummary, "Sum_Pop_1524T1", "", "Pop_1524")
except:
pass
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Lot's of other useful way of updating a table using the Fields Toolset within the script - Alter Field, Calculate Field etc