This thread is frustrating to read! If you made some changes and adjusted your spending, you could easily get out of debt quickly. But you seem to be fine about having the debt. I think from reading your posts you have a spending problem.
You buy spares of clothes, in case you get behind with the laundry, in case they lose a pair of gloves - this is so unnecessary.
You spend hundreds of pounds that you cannot afford on swimming lessons, when you could either teach them yourself for very little, or wait until you can afford to pay for lessons.
You spend money on school trips for primary school children, another unnecessary thing when you clearly cannot afford it.
Your DH is supporting two adult children in uni, when his wife has an out of control spending problem and as a household are in debt that you are struggling to pay back. I get he wants to help his children out, but the crux of the matter is, he cannot afford to. He's on a relatively low salary - you said a high earner, but at £2800 net, that is still only average. Surely his adult children can work part-time jobs whilst they study to help support themselves? Even if it's just until their dad gets out of debt.
If I were you, and I know this advice will fall on deaf ears. But I would spend the next 6 months buying ONLY the essentials, and I mean essentials. No spare clothes for the hell of it, you can make do with whatever shoes you all currently have, no expensive foods, no clubs for the children, literally only the bare essentials. Use every single penny saved to through at your debt, and I would be confident enough to think you'd have most, if not all of it paid off by then.
The thing with debt is, you got to want to get rid of it to get yourself out of this hole. Sadly, I don't think you're in that place.
Please watch some Dave Ramsey on Youtube. I feel like I tell people this a lot on here recently, but just listening to a few of his shows, and hopefully you'll realise how stupid you're being, and give you the want to get yourselves out of this mess.
I'd also suggest upping your hours at work, if at all possible, I know you've a 1yr old so not sure what childcare you have in place. Or perhaps you could get a weekend job/work on your DH's days off. Just as a temporary measure 6-12months or so.