I have just done something dreadful... have used a payday type lender to borrow £100. The interest is phenomenal (you really really would not believe the amount). But over six months I am repaying twice that! 
I work part time and have a child with special needs who I care for the rest of the time hence not working full time. I am a single parent (past three years) but my exH gives me £200 most months for our child. His work is seasonal so in August last year I got nothing. When we split up it caused problems with debts we had between us. I could not pay alone and he was virtually bankrupt at the time - hence I now have a shit credit rating and nowhere else to go apart from these sub prime lenders.
I get DLA for my child and also extra child tax credit but even so with the rise in petrol/food etc my outgoings have increased a fair bit. It didn't help that the freezer packed up last week and I lost probably about £100 worth of food squirrelled away for lean days. I am insured but this all takes time. In addition the Tax credit people decided they may have overpaid me (or might NOT have done - they are not sure but have decreased my tax credit by £100 this month and next until they can do their final workings out.
So - new fridge/freezer (actually got a second hand one off of ebay), all food to be replaced AND £100 down.
So I have a week to go till payday and no money - mobile phone payment goes out on Monday (£30) and I need this so school can contact me if necessary.
Borrowed £100, lender took off £15 "bank credit fee" and I will repay this over 5 months )although am confident I can clear it in less.
It's crap but at least we can eat. Could'nt ask exH as he lent me money for the fridge/freezer which I have to give back next week when I get paid.
Anyhow - this month has been a bit crap BUT I am confident I have enough coming in to cope with bad months. I think that the issue is if I have money in my pocket it gets spent - loaf of bread here, pint of milk there, petrol - maybe a sandwich. I don't (or rarely) buy or drink alcohol. I don't buy books or CDs except via charity shops or ebay. I even buy all my clothes (barring undies) from ebay.
I suppose what I am asking is how others manage financially for these months. How much do you put away as a percentage?
I DO give to charity shops as well (perhaps I should be ebaying) and apart from that I sponsor a child in the third world but that's just £15 a month and I am prepared to forgo other things to do this.
I am in a HA house so rent is lower than if I had to rent privately. I am not entitled to housing or council tax benefit as my salary +working and child tax credit takes me over the threshold.
To be honest I feel a bit of a failure for using this company to get through the next week but have to ensure everything stays normal.