Ok OP, I’ve just been served with an S21 as my LL is selling up.
The S21 gives a date when they want you out. They can’t kick you out unless they obtain a court order which they can’t do until the S21 date has passed. Court orders can take 4 to 7 months to get.
This is important, do not move out until such time as you’ve secured alternative housing or you’re served with a court order. If you do move out before either of those things have happened then the council will judge you to have made yourselves intentionally homeless and they will not help. Keep looking and keep paying what rent you can until then.
Get yourself down the council asap with your S21 and make a homeless application. You’ll need to provide documentation, relevant evidence and bank statements but they’ll advise you on that. You are legally entitled to a decision in writing spelling out what if any responsibility they have towards you under their prevention duty. Also apply to go on the general housing register if you haven’t already done so.
Get yourself to Shelter. In my area you have to be referred by CAB but I don’t know about where you live. This is important because the council will find any way they can to wriggle out of helping you. If there’s even a shred of a reason to refuse they will. Shelter can advise you on how you can access legal aid (if you qualify) as you might need legal advice and potentially you might have to take the council to court.
Is there a floating support in your area? We have one here and they’re very good and I know a lot of places do. If so get in touch with them. They are there to help people like you. If you need to be referred then find out who by and keep on at them until they do. Ours you can self refer but I don’t know about others.
Arm yourself with as much information as you can. You need to know your rights because the council aren’t about to tell you. Throw your net out as far as you can and get as much support as you can squeeze out of doctors, SS, whoever. As PP have said, make sure you’re getting every penny in benefits that you’re entitled to.
Good luck. I know how you feel and it’s nauseatingly scary.