I'm on my phone so forgive me for not individually quoting but I'll try to answer everything.
Just to reiterate first, our circumstances are exactly the same as they were under tax credits.
We have no savings, just what's in the bank to pay the bills, so the amount varies on a daily basis but it isn't over 6k and never has been.
I'm not sure how I can pin point where the loss is occurring or what that means exactly. Under TC we received 13 4-weekly payments of £531; a total of £6,903. We have just received notice from UC that our award, which I understand is paid monthly, is £421; a total of £5,052. The difference to our annual budget will be a £1,851 defecit.
I will double check the info on our UC account to make sure we've not accidentally put any incorrect information in but having just had a quick phone call with one of their staff the figures they quoted back to me seemed to be correct.
We are not paying off an advance.
Pay frequency may be the issue. My DW gets paid weekly and I get paid 4-weekly, therefore there will be some months when she has a different number of pay days and one month when I have 2, so I guess that our UC payments will go up and down and my calculations, based on 12 equal payments (I've nothing else to go off), will be wrong, though the last time I got paid twice in one month was December and an extra payslip in one month of my wife's income wouldn't make too much difference I'd have thought, but I'm grasping at straws here.
Does anyone know if our claim, which we began mid Jan and have been informed of the amount we'll receive today in Feb, would have been calculated using December or January earnings?
Overall I've got the feeling that one way or another we are going to have to do some serious belt tightening, and not having a definite figure that we will receive each payment is going to make budgeting a bit trickier.