Thanks gmr4evr1, this works

Just for completeness I would like when I hit save it to revert back to the 'Summary' tab and select cell A1 - I have edited the formula you provided can you point out what is wrong?

Private Sub Workbook_BeforeSave(ByVal SaveAsUI As Boolean, Cancel As Boolean)
Sheets("Headcount").Select
If Columns("C").Hidden = True Then
Exit Sub
Else
Columns("C:E").Hidden = True
ActiveSheet.Protect Password:="password"
Sheets("Summary").Select
Range("A1").Select
End If

End Sub