Does husband need to take responsibility for this?

It’s sad and frustrating to read this. From your point of view you might see your life as being a positive, stable life but to me it comes across as really out of control with disaster about to descend. I feel for you having this to sort out. Maybe shock him by piling up things to sell (and mean it) and start refusing all new bought items.

You have described my step dad to a T
He died leaving £27k of debt on cards and in loans.
It’s those left behind that pick up the pieces 🥺

So he spends what you earn or is your wages separate?

Still one good thing might come out of you both dancing around the issue. It'll fuck his credit score. No more loans

You’re using positives to describe his behaviour but I find it quite selfish! Im
really greedy (and overweight!) and me treating myself and my family to food is me being extra greedy! Same with buying presents, easy to do and everyone loves you.

Making a healthier tea, going for a walk, playing with an old board game - all sounds twee but that shows real care. Anyone can spend money and it sounds like you don’t have it to spend.

He's a hoarder, shopping and dopamine addict - the pleasure is in buying more things, buying expensive things, owning and presenting new things to people, having more things around the house, being the person who goes round the supermarket putting the so-called luxury items in the trolley.

Just open the damn letter. See what he owes - that'll make it real, which is what he's avoiding by not opening it, and is quite possibly contributing to his buying as he's trying to block out the thoughts about it by going for the dopamine hit of buying more bloody Stuff.

He won't appreciate the reality check and will hate being told that he can't pursue his addiction to a few moments' buzz - but you've got to do it before he drags you into poverty, as there is no off switch and he will continue spending until you have less than nothing.

You're both burying your head in the sand here. Tell him to open the letter now and face this shit head on or you'll lose respect for him. Stop with the don't want him to feel unhappy crap. Your needs are just as important.

This is a proper come to jesus conversation OP. You both need a good talking to.

He’s addicted, same as an alcoholic or gambler. He needs help. Would he let you take control of the finances? I think you’re right in that you need to set the example. Has he understood how awful the kids’ rooms look with all the overflow of stuff? I mean, has he really SEEN how bad it is? I would do a hard re-set, chuck out excess/stuff that no longer fits/gets played with, like the Stacey Solomon programme. Sell, donate etc, you’re going to need the money.

Crossposted with you OP. Sounds like you've started to see what's wrong. Can you get help/advice to support you in making the change?

Op , if you can't sit your partner down have a conversation about how their behaviour is impacting your (and the kids) life negatively then you have a problem. You should be able to do this with each other and have that person make self motivated changes with support. I've been where you are and it ended in divorce. I am now married to a person that takes responsibility for himself and it is not only refreshing , but also vital.

I've tried.. But it seems so hard on a little kid..
Again, OP, you are part of the problem here. I had to do this with my DD because we lived in a tiny house and had no more space. I explained it simply, she understood and was able to choose things she no longer wanted. With clothes it's easier. If they are too small, get rid.
You are not helping your children by being this soft. If they were sick and needed treatment, you wouldn't refuse it because it might be a bit unpleasant would you. Well this is for their mental health. And yours. And the long term resilience of the whole family.
You need to change your perspective on this urgently.

Have you actually told your husband all the things you’re telling us? Have you brought him into the room when you’re trying to find space for stuff and said “Look, this has got to be a wake-up call: I love you and I know you love to be generous, but we have far, far too much stuff; this is over the top and it’s not actually making any of us happy now. It’s got to stop. Do you think maybe it would help to have a think about why you’re buying all this stuff and why you can’t stop? Because it’s at the point now where it does feel a bit like a shopping addiction and that’s really worrying me.”

PS: use the piano.
get it tuned, open the lid, learn. Encourage the children to learn.
At least you might feel a bit more in control.

My friends husband is exactly the same. Although he was telling her he had paid the red council tax and rent bills that were coming through. He was spending money on new cars, phones, food etc; they were evicted a few months later. Open the letter. Get a plan in place ASAP before this spirals.

It's not harsh on a little kid to make their life more pleasant by getting rid of crap.

Seriously, go through all of their stuff. Sell anything that no longer fits, put that money in an account of your own, not a joint account.
Sit with them and work out what toys, games and books they don't use/play with and sell those too.

I'd be making steps towards restricting his money, too.
and force him to call hmrc.

If he's got previous for racking up big bills that mummy and daddy bail him out for, hes not likely to stop doing this op. I personally couldn’t live like this with the uncertainty of his financial incompetence

@NewDogOwner why is it the op's responsibility to do this? This needs to dropped at his feet , respectfully and with support and encouragement obviously.

I think you're seriously under reacting op.

He's overweight and in debt. This could have severe consequences for you and your family. Just because he's doing it with a smile on his face it doesn't make his behaviour any less damaging.

You need to be firm , and mean what you say. He can't be left to it as he's not a single person. That's selfish of him to ask of you.

Can you work out why he is like this? It could help. Did he grow up poor and is making up for it? Did he grow up wealthy and with a family who behaves similarly? Once he thinks about what need this fills in him, he can try to work through it or find a better way to deal with his motivation.

Time for some tough love OP.
You first - you are enabling him.
He has a real problem and your reaction is to wait for him to sort himself out because you don't want to make him unhappy.
If you lose your home you will all be unhappy. Open the envelope. Now. In front of him.
Do your children enjoy being swamped with stuff, seriously? They are going to grow up with the same inability to regulate their spending/eating.
If you can't do it for your own sake or your husband's sake, take control for their sake. It's no way for them to live.
And you can start by having a one in, one out policy. They do not have any room for any more stuff, so every time your DH buys them something, you take an old toy/game pair of jeans and donate or sell it on vinted etc.
Do not let their stuff start to creep into your space. Stop that right now