Citizens advice are supposed to be the ppl to go to but it's all quite complicated really.
If you don't work you will get Income support, Housing benefit and Council tax Benefit but anything the FOB contributes will be deducted from the amount you receive.
If you work you will be caught in the catch 22 situation of trying to guess.
If you are in the situation where you need to claim tax credits, you can use the online calculator or call them. You don't have to make a claim, just tell them you are trying to work it out for the future. If you get somebody unhelpful, just call back. If you get the right person they are really helpful.
If you get tax credits you will still get HB and CTB.
Your minimum entitlement is:
Money for you from tax credit/income support (about £50pw depending on age)
Baby's money (about £50pw with a preimum of about £10 pw if under 1, and Child Benefit which is about £15pw)
If this is your only income (or you don't earn much) you will get max HB (there is a set allowance depending on your postcode - you are "entitled" to claim for anything up to a 2 bed flat if you have one child).
And full CTB.
Anything you earn up to a certain amount is not counted to calculate your entitlement. Anything the FOB gives you will. (If he gives you say £55 a week, this will reduce your benefits by about £50pw)
Sorry the figures are hazy, but hope it helps. If you want to send me a message with more of your details I could give ou exact figures...