Dear Lewis, I really empathize with your situation--I do think you did the right thing by returning for the children and I imagine that they are very grateful for that!
I will give you my take on your situation. First priority--the children--they need to be separated from that drinking environment. How about consulting legal advice as first step (I am in U.S. and I know that the laws differ somewhat in the U.K.). Find out how a legal separation works. Step two--Ask her to go into treatment and AA program to maintain her sobriety. She may well reject this--but, she might not if she see that she might lose her marriage and family.
In any case, she will be faced with separation; divorce; loss of child custody---or get sober. This can be a powerful motivator for a mother. It is the reality, though---if alcoholism is to be eliminated from this home.
About the domestic responsibilities--one simply has to engage household help for some of it--and, as suggested by another poster--you all will work it out as a family team. Most children can handle more responsibility that we give them!! It won't hurt them.
Of course you will need lots of support--everywhere you can get it. From professionals--SR--Alanon---friends/family (if possible).
Lewis, there are options. Maybe, ones that you never wanted to consider before.......but, sometimes we have to do what we must do---even though we didn't have it in our dreams.
Many husbands and fathers have been in your shoes. You certainly are not alone!
dandylion