So it seems that the problem was with the replace statement. Modified code thus and this seems to work, hopefully this will help others as I found several other posts showing that this macro didn't work for them but without a clear/simple solution.
Code:
Sub ChangeOLELinks()
Dim oSld As Slide
Dim oSh As Shape
Dim sOldPath As String
Dim sNewPath As String
' EDIT THIS TO REFLECT THE PATHS YOU WANT TO CHANGE
sOldPath = InputBox("Enter Old Project ie: \Development\", "Old Path")
sNewPath = InputBox("Enter New Project ie: \Test\", "New Path")
On Error GoTo ErrorHandler
For Each oSld In ActivePresentation.Slides
For Each oSh In oSld.Shapes
If oSh.Type = msoLinkedOLEObject Then
Dim stringPath As String
stringPath = Replace(oSh.LinkFormat.SourceFullName, sOldPath, sNewPath, 1, , vbTextCompare)
oSh.LinkFormat.SourceFullName = stringPath
' set update mode to auto and update then set it back to manual
oSh.LinkFormat.AutoUpdate = ppUpdateOptionAutomatic
oSh.LinkFormat.Update
oSh.LinkFormat.AutoUpdate = ppUpdateOptionManual
End If
Next oSh
Next oSld
ActivePresentation.Save
MsgBox ("Done!")
NormalExit:
Exit Sub
ErrorHandler:
MsgBox ("Error " & Err.Number & vbCrLf & Err.Description)
Resume NormalExit
End Sub