oh it’s autumn, Halloween is also coming we’re going to need autumnal cushions and throws in the living room, smelly candles and reed diffusers, kids costumes, decorations
Did you buy these things last year? What happened to them? OK, the candles and diffusers probably got used up, but what about everything else? Seeing as it sounds like this is how you've always been, don't you have these things from last year, that were only used for a few days so still in perfect condition? Surely you're not buying new every year? That would be terribly wasteful, both money and resources. Don't be that person.
Set a limited budget after all other costs have been accounted for and, if you don't have room to store things that you will use year on year, look in charity shops or ask around for outgrown costumes.
Likewise Christmas. We're still using the same set of decorations I bought for our first Christmas in 1995. We have added a few things along the years, but not many and they're just kept in a box in the loft and brought out each year, I can't imagine buying a load of new things every year when we still have perfectly good ones already. And it isn't like they were expensive, they were in the sale at BHS (remember them?).
But on the money that should be left over, is some of it going on annual and irregular expenses like insurance, car costs, white goods replacement? But anyway, you need to save for these things before spending on trinkets so make sure you do that, put the money into a savings account on pay day, so you don't have it sitting in your current account where you think you can spend it. Also holidays, Christmas etc. It's likely that all these costs will average out at a few hundred pounds a month if you go on holiday and run a car so don't underestimate them and plan them into your budget if you haven't already.
The other potential big use of money is food and drink out of the house. A coffee on the way to work and lunch from somewhere like Pret could cost £10 a day or more, which is £200 pm or nearly £2.5k pa, which would pay for a holiday. A few quid here and there really adds up for anything you do regularly.
Assuming you pay for most things by card, look through your statements for the last few months - most banks allow you to categorise your transactions so you'll be able to see what you've been spending on.
Maybe separate your money into different accounts, or pots within the same account. Have standing orders and direct debits that cover bills, food and travel, savings for the annual and irregular expenses mentioned above (plus an emergency fund and for any large planned purchases like home improvements or car replacement, all this is more important than new cushions for autumn or coffee on the way to work) and then what's remaining is spending money for non essentials. Perhaps separate this out so you cover DC costs, personal money for each of you and possibly 'house money' although you may decide that cushions, throws, candles and diffusers are your expense, seeing as it would be a rare man who would actively choose to buy these things out of his own money.
But definitely see what you can sell and put your energies into doing that instead of buying. Remember that influencers are promoting their 'brand' and are being paid/get things for free to show them to you so you buy them too. Don't fall for it.