If you're serious about changing things, you need to analyse your spending and budget. You might find that the cost of your essentials has gone up, so some of the money will have been accounted for that.
If you've been working more, you've probably spent more on petrol, parking etc which can't be avoided as is a cost of working. For the 'missing' £450 it should be easy to find. Download the transactions from your bank account/credit card and use the assigned categories to analyse where the money's gone.
Did you really need to buy so many birthday presents for friends and family. Most adults would really not miss exchanging gifts or exchange very token gifts like a small bunch of flowers/bottle of wine.
But I don't understand how people can say they don't see how the odd £20/30s add up to hundreds of pounds if you do them a few times a week it adds up over the month, it's basic maths that we're all capable of.
You also need to account for annual and irregular expenses because it's just regular expenditure that will happen sooner or later, so you need to put money aside for this and don't look on it as 'savings' because it's not money that will build up for the long term. Christmas would fall into this category, likewise the wedding. Presumably you've known about this for a while, so you should have started planning on how to pay for it.
If you want to save money 'just because' or for an emergency/retirement etc, you need to put it away before you consider spending on non essentials. Then you can't spend it, but if you arrange your money so it is allocated to cover all of:
Essential direct debits
Childcare, children's activities
Food and travel/fuel
Annual and irregular essentials like school uniforms, opticians, dentist, prescriptions, insurance, car servicing/MOT and things you would like to have like Christmas, holidays, birthday gifts, wedding attendances, mini breaks etc
Savings for emergencies, car replacement, retirement/just because.
Obviously most of the above is essential although you have to cut your cloth with things like Christmas, holidays, gifts, cars etc so you might not be able to spend as much as you'd like on all of these.
But you do want to aim to have something left to spend on personal non essentials and leisure like art materials if that's your thing. And as long as you're not spending hundreds of pounds on this when you already have a cupboard full of similar that you never use, it's not a ridiculous luxury, it's a normal expectation.
Anyway, the Moneysavingexpert Money Makeover is a good place to start changing how you see money and will free up more to spend on nice things. You can even get a free £100+ a the moment by changing your bank account. Get the weekly email for regular reminders and tips like this.
www.moneysavingexpert.com/family/money-help/