No heating or hot water for 3 days, gas man due this evening.
The water pressure is too low. It's a common problem apparently.
If your boiler has a readout panel, google the error codes. I did. If it is low pressure, you can sort it so easily with a spanner, honestly.
On Income Support and with a child you are eligible to claim an emergency payment/crisis loan/budgeting loan whatever it's called lately assuming it wasn't part of the welfare reform which scrapped lots of these types of grants.
It's an interest free payable loan with tiny weekly repayments of a few pounds (or more if you wish) with which you can buy a heating appliance (research for the most economical) for example. I think the portable gas heaters are the most economical to run long term.
Electric blankets are not very expensive to run and a double can be bought for £8 at the moment in QD Stores, if you have one local. Good for the sofa as well as the bed.
I have a spare portable air blower heater which I can send you, if you want to PM an address. 'Poste Restante' to your local post office if preferred (anonymous).
Having said that, I'm on key meters and it cost me over £7 just to keep it on for 5 hours today 
I'm really sorry you're going through this, I thought 3 days without was bad enough (including one poorly 6 year old).