I've no idea what ES means either. But on the original (on ancestry) half the page's entries has that ES marked on it so it's probably not significant. 
BUT.
you are my hero janet.  
This baptism
Baptisms: 19 Sep 1865 St Mary, Lancaster, Lancashire, England
Ellen Colewell - Child of David Colewell & Betty
    Born: 31 Jul 1865
    Abode: Bridge Lane
    Occupation: Labourer
and this birth certificate on lancsbmd. 
COALWELL    Ellen   Lancaster   Preston   BLEASDALE   LAN/33/90
(Colwell spelling variations 9 and 10! to go with - Colwell, Corwell, Calwell, Calwall, Cowell, Coldwell, Caldwell & Cauldwell ) link the families together. 
So even if I've no idea where they are in 1841 or 1851. Why the igi has that marriage at crosthwaite, kendal when the GRO index has it in cockermouth or where the brother is in 1871 if he's marrying in preston in 1877 or  any other of a few random questions (more to be determined later). 
This is the first breakthrough I've had with this nightmare family in quite a long time.
Thank you, thank you, thank you.
pete