What's the interest rate on the car loan? If the loan allows, it's probably worth putting some of your spare money into overpaying the car loan, to save interest, which is likely to be higher than any savings, except perhaps the bonus elements of the Help to Buy ISA so keep up with that first.
When the loan is paid off, are you planning to keep the car long term after that? If you can manage to do that, your plan should be to save for your next car, and going forwards, only pay for cars out of savings, not with borrowed money. It makes a huge difference.
Whether or not the £1100 a month 'spare money' is a lot depends on exactly what it's supposed to cover. You've already mentioned food.
What about annual and irregular expenses like insurance, Christmas, car repairs, new washing machines? Are you putting money away out of the 'bills' money, or does that also come out of the £1100? If not, it then shrinks further.
What about your DHs fuel for work? Any essential travel for you and DC - medical appointments etc, and what about things like eye tests, dental, hair cuts?
Sounds like a time to have a really good look at your budget - even if you don't earn money directly, you not working might mean that you have time to keep a really close eye on the family budget and make your money go as far as possible, shopping around etc, which can have the same effect as earning money by working, but is then lost because you're time poor so spend more because you have to do thinks quickly, which is usually more expensive. You mention a high risk DC - if they have additional needs, you may be entitled to carer's allowance.
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