The only thing I can say is that you will find the strength in you to go through this and ensure your kids are ok.
It is unfortunate that this is happening, but the age of your kids will actually work on their favour, they will find it easier to adapt to the new situation than older kids do.
It is said that it is not divorce that damages children but all the nastiness and arguments that may come before it so, it is understandable you want things to be resolved more quickly. It is the uncertainty that is unsettling, once you know how the things will change you will feel more in control. Same with the kids, do not let them know their dad is leaving until you know when and where exactly contact will take place.
As for you, this is the time when you need to accept ANY support that comes in your direction. Don’t suffer this alone, those people that approach you to try to help may well become part of the so much needed network of support you need to your side.
In terms of practical things... check entitledto.org.uk if you qualify for universal credit. If so, apply for it as soon as possible, you don’t need to wait until he moves out, as long as you are not acting like his wife, ie cooking and doing his laundry, it is ok.
Hang in there 