The financial flow chart can be used as a 'to do list' of what's needed in what order, so if you see any gaps, that's what to focus on.
With a mortgage of £300k at 45, that's quite a lot left to pay so you'll probably expect to be working until state pension age or quite close to it? Also having DC, university costs etc.
What does your DH earn and what's his attitude to money? Is he better or worse than you/what you're aspiring to? Do you feel that separate finances are fair? Also, unless your DH earns over £80k after pension costs, you're in the position where you're entitled to some CB but not all of it, so are you on top of this to repay as needed?
I would focus on setting a really comprehensive budget and sticking to it. Moneysaving Expert has good advice on this. Also minimising costs on things like phones and broadband, if you don't regularly check the prices of these, you can pay way more than you need to. If you get their weekly email, you can get ongoing reminders on how to improve your finances.
Budget Planner: how to manage your money - MoneySavingExpert
As for saving and spending, put away money for planned and irregular expenses before seeing money as available to spend - set up standing orders to come out on pay day. If you think about Christmas, holidays, insurance, car maintenance, replacement of white goods etc etc, this can be a significant amount of money, hundreds of pounds a month, possibly over £1k. So you need to account for this before seeing money as 'spare'. Also any planned big purchases like car replacement or home improvements. If you have a decent income and plenty disposable, you should largely be able to fund these without borrowing.
I would split my money into different accounts - a bills account, savings for the things mentioned above, day to day family essentials - groceries, travel/petrol, sundries like presents if DC go to a party etc, things you can't avoid paying for, although it's worth considering whether you're overspending on these areas, your grocery bill could vary by hundreds of pounds a month depending on what you're buying for example.
Then you need some personal money for you, that you are allowed to spend without worrying. Set up a standing order to a separate account, the amount is whatever is affordable after all essentials and family costs are accounted for - you can spend this on whatever, but when it's gone, it's gone. But you don't have to spend it all in one week/month - you can just leave it to roll over until you see something you want later.
If you don't already have a suitable account, look at Chase, Kroo, Starling, Monzo etc, you can set up an account quickly in the app and get a card that you can add to your google/apple wallet straight away. Or I think you can set up another space in your Revolut account.