OP - it sounds like you've reached a point in your life where you value financial security and stability, and you are ready to take serious steps to pursue it. You can do that with or without him. The most important thing is that you do it.
It doesn't matter if you've had problems managing money in the past. I was atrocious with money when I was younger. And I had a couple of partners who were equally bad (actually - even worse).
If I had stayed with them, they would have dragged me further down the hole. That doesn't mean it has to be the same for you - but if you're going to financially thrive AND stay in the relationship, you are going to have to hold yourself accountable. You definitely can't just rely on him to sort it all out, or keep plodding along. You need to properly sit down together and go through your finances and create a plan of action. If he's not willing to do that, you have a big problem.
I'm a dreamer too, so I can relate to your partner. BUT I also know that I can't experiment with businesses unless my finances are stable. It's out of the question. This means that I'm currently holding off on business ideas I want to explore, because I'm working on more urgent things like saving for a deposit, etc. He doesn't need to give up on his dreams, but he does need to get realistic about his responsibilities and limitations.
The problem with Gary V and the like is that they brainwash you with stories like "I was broke, in debt, not even a penny to my name - and I became a multi-millionaire by taking a chance". I used to listen to all of those people. It completely gets into your head and makes you feel like you're a complete loser if you DON'T try.
Ultimately, what I think is this -
You need to get in there, open up a spreadsheet or draw a chart on a piece of paper, and work out what your household budget is. Have you ever done that? Your income, his income, and all of your outgoings? Car, TV, bills, etc.? Do you have a separate bills account? Or do you just each have your own bank accounts and pay individual things?
You can then look at what you could cut down on - and you can see what you actually have in disposable income at the end of the month. Whatever that amount is, some of it can be set aside as spending money for each of you. He can buy Tesco lunches with that if he wants, and you can buy whatever you want to buy. Some of it should also go into savings - even if it's £25 a month, or whatever.
If you look at the spreadsheet and realise you actually have no disposable income at the end of each month, then you need to address that by reducing costs, making more money, or both.
The bottom line is that you need to be a team on this. Nothing wrong with him being a dreamer. Dreamers can have many positive attributes. But the foundation of your financial relationship - and your life together - needs to be stable in order for him to pursue his dreams fairly. Otherwise you're not a team at all. You're each on your own agenda and may as well not live together.