Just wanted to say how well you're doing tackling all this head on given your depression and difficult circumstances.
One bit of advice from me would be when you are dealing with Stepchange, they will (or may already have done this with you) get you to complete an income and expenditure form, so they can see what you have left each month, from which they will then work out how much each creditor is entitled to.
When you do this, don't underestimate your outgoings, be realistic. Bear in mind emergencies that can arise, things like birthdays and Christmas (even if they are small amounts), haircuts, if your son outgrows his shoes or rips his trousers, prescription charges here and there, etc. You absolutely need to make sure your budget is one you can live on reasonably comfortably so you don't have sleepless nights! The trick with being in debt and being able to pay it off without needing to borrow more is having a cushion, however small, for the unexpected things life throws at you.
Of course we should all be responsible and pay our debts back but you need to look out for you and your son first and foremost, before your creditors. They can wait if they have to, in my opinion. It's better to have a trashed credit file then a mountain of stress and going without basics in an attempt to keep up.
Good luck with it all.