OP have you applied for help with your utility costs? There are extra grants available for vulnerable people, so worth a shot.
Also you can get a special broadband deal, which will be a bit cheaper than commercial contrats.
Unfortunately Sky is unaffordable, but you can get nearly the same service from Now TV for far less - you don't even have to pay the headline price as there's always deals available. We've had it for years, and usually pay £2-5 a month for the entertainment package.
There's also a special water tariff that you can apply for, if you qualify, which it sounds like you would do.
If any of the above applies, you can make a few savings that frees up a bit more money to feel more comfortable. If you're really struggling, then utilities are lower priority than housing, council tax and an appropriate amount of groceries. The amount that's considered reasonable is probably quite a bit more than you think if you're used to juggling a low income. Obviously you can't expect to walk round Waitrose throwing everything in your trolley that looks nice without looking at the prices, but you are allowed to buy sufficient food, and washing powder and calpol if needed.
For water and other utilities, tell your supplier that you can't afford to pay and ask for help and see what they offer. They should help you.
Have a look at Moneysaving Expert for a systematic run through of reviewing your finances and help with making the best of your budget:
www.moneysavingexpert.com/family/money-help/
www.moneysavingexpert.com/utilities/how-to-get-help-if-you-re-struggling-with-your-energy-bills-/
Also perhaps see your DM less, if you drive to meet her, tell her you can't afford the petrol. You're right to not expect your DM to help you out, but it sounds like she is able to and it's not nice to see her flaunting her comfortable lifestyle while you struggle. Does she work? Could she help you with childcare by just minding her DGC some of the time to reduce the amount of childcare you need to pay for?