The best “hack” I have is simplify your finances. Have one account, a modern one like Monzo so it gives you proper spending analytics (and no bullshit fees).
Avoid subscriptions, direct debits, etc. You need to be in control and pay things when you want and can afford to, not when the company wants. If you’re in a bad place and can’t afford to pay all your bills this will also let you control which ones you want to pay (based on how much you need the service, what the non-payment penalties are, etc) instead of them being paid on a first-come-first-served basis until your money runs out and an actually important bill bounces.
If you can’t avoid subscriptions (because it’s the only option) then choose for the yearly payment option; this means you only get a surprise every year instead of every month. If you can’t afford to pay it in one go then maybe rethink if you really need it.
Go over your scheduled payments and see if there’s anything unnecessary. Charities, etc can go. If you’re in debt you definitely shouldn’t be giving away the little money you have for free. Actually, charity direct debits can go in any case, debt or not - make one-off donations instead if you really want to.
Anything that you do need, see if there’s another provider that can either provide you the same service for cheaper, or a better service for the same price (if you can’t pay less then you may as well strive to get more value out of that money). Avoid bundled deals like phone insurance, etc as often you won’t actually need it; and that’s the business model of those “deals”, these “perks” are more about adding an extra bullet point on a list so you think it’s a good deal when actually you don’t need it in the first place.
Oh and another mistake I see a lot of people make is the TV license. You don’t need it. It’s probably the worst deal in existence, paying a fee for the “privilege” of being blasted with ads 24/7 with the occasional bit of filler content. Netflix or similar is much cheaper and provides better value, not to mention the endless free entertainment you get on the Internet. You can also choose to put Netflix on hold if you are in a bad situation, where as a TV license is yearly; so you pay even if you don’t actually want to watch any TV for that particular period.
Don’t fall for the scams like cashback or similar perks from legacy banks; they’re a lie to get you to stay with them and end up getting hit with charges at their earliest convenience (and if you’re in debt you might very well end up with a bounced direct debit, etc). Being in control of your finances is worth way more than 20£/month worth of cashback.
Finally invest in yourself & your career and always strive to earn more money; this will allow you to pay off any debt you have and reduce your reliance on debt in the future.