"Look after the pennies and the pounds will look after themselves" maybe an old saying, but is as true today as it's ever been.
It basically means you have to get used to money saving being a habit, whether big or small amounts. It encourages you to shop around for better deals, look for discounts, compare prices, and most importantly help you get into the mindset of "Do I actually need to spend this money?" as a thought process for literally everything.
The more you shop around and think about things, maybe seems to be small amounts, but the more you get into the habit, the more you notice how and where you can get discounts/deals, etc.
For supermarket shopping, get all the club cards etc. For general spending, get a cash back current account and credit card. Use comparison sites for insurance, utilities, car insurance, holiday insurance, breakdown cover, etc EVERY year. Get your OH to buy his lunches using chain/supermarket meal deals and their club card. Get him to swipe his Greggs app whenever he buys a sausage roll or coffee there to accumulate to freebies!
Always google for discount codes etc if thinking about going to restaurants, attractions, or buying from websites. You can usually get a 10% discount code just for signing up to a newsletter on many sites. You can usually find/apply for discount codes for chain restaurants. You can often get discounted entry at attractions by buying a rail ticket (often you can get big enough discount by buying a cheap train ticket you don't even intend to use - i.e. a £2.50 ticket can get you a tenner or twenty off admission for some major attractions!).
Think about what subscriptions you have and whether you need them. I.e. Sky, Spotify, Netflix, etc - can you change your internet/TV provider and get some subscriptions free/packaged instead of paying separately?
More than anything, you need to know where you money goes, both yourself and your OH. You need to track and analyse spending. Most modern banking apps will either do this for you or will help you do it via download options etc. Don't use cash as you don't have a record of where it goes. When you know what you're spending, you can start making wise decisions to reduce it.
As for your OH's business, he needs to get on top of his numbers. He needs a decent book-keeping system like Freeagent which will record and analyse the numbers from automatic bank feeds, and then automatically give him the numbers for VAT, PAYE and business tax as they accumulate through the year, so he knows where he stands. He needs to be on top of invoicing his customers, to make sure he invoices everything and that all his customers pay him on time. It's far too easy for self employed to ignore this detail and cobble it together at the year end, only to find unexpected tax bills, or some customers havn't paid and now disappeared etc - just wasted money due to laziness and inefficiency!
Also look around your house etc and sell everything you no longer need. Clothes, childrens toys, CDs/DVDs, books, etc. For low value items, create packages/bundles and get them on Ebay.
Lots of small savings/incomes soon build up into worthwhile money left in the bank!
Goes without saying not to waste money on expensive cars/car leases when you could get a much cheaper car that does the same job.