The question is mate...
What will England do, when the Scots leave Britain>? Not the other way around.
England, or the Conservative Party, which is actually looking forward to the split up, has already done as much damage as it possibly can. Little wonder of the coming split.
England will be much more diminished in the long term.
We will lose our Trident and main submarine base. These will not be replaced in England and will whither thus, I predict.
We lose access to the Scottish regiments that served us all so well (every single war memorial in the British Isles tells us so even if you think I lie).
We lose the shipyards either side of the belt. We lose skilled manpower. Oil and Gas revenues and security from that. Large areas of ocean and food therein. I could go on and on.
We lose all and every way when it splits. Britain dies, that's the point.
What do we gain? Already a lot of talk in the North of England about this in the last few days and you wouldn't want to hear it. Federalism may come yet to the remainder after all. I don't think things will be rosy at all for England after the split, and I see a lot of trouble ahead for all of us.