To not take baby to visit inlaws?

Don't engage. Reply "the reason why is irrelevant, that's my decision and that's the end of it".

Is he on the birth certificate?

Don’t engage with them, block their numbers as you have no reason to have them. At most offer to meet at a coffee shop or park in town so you can leave when it suits you. Bet they don’t bother. Ex sounds like a waste of space and longer term you may want to get supervised contact set up.

Your ex is going to need to be doing some step up visits himself. Once your baby is older and he's comfortable with childcare, he can arrange for his parents to visit him on his custody time. Get a court order regarding custody before that happens.

Do not take your 4 month old on a train to them. That's fucking ridiculous. Block them if they harass you about it.

No, they are being entirely unreasonable and showing no consideration. As you say, they are allowed to visit and that's where it ends. If they can't be bothered, why are they insisting you make all the effort instead?

Just live you life as you wish, it's not your job to keep everyone's life easier and simple.

I wouldn’t be making an effort to go to in-laws if I wasn’t with the kids’ dad. The assumption that the in-laws would expect me too is alien to me. They should just be calling you to see when is convenient to pop over. And when the child is older, when can they have the child over for the day etc..

They need to make all the effort to see their GC.

Nope, you aren't at their beck & call.

I'd tell them they are welcome to visit, just to give you a call first to ensure you are in, but travelling on public transport for hours with a tiny baby is not on.

You're not being unreasonable at all. This line from your post caught my attention: "apparently I could get a train or ask one of them to pick me up." If they're willing to drive and pick you up, then they can simply cut the picking you up part out of the equation and visit their grandchild once they've driven to your house.

It sounds as though they, along with your ex, are being difficult just for the sake of it. "Everyone else" absolutely would not get on a train with a four month old! The fact that they keep cancelling or turn up late shows how little effort they're willing to put in to seeing their grandchild.

Stick to your guns and don't budge an inch. I hope that you enjoy every precious moment you have with your little one OP.

Nope YANBU. Standard procedure is for family/friends to visit new mum and baby in their own home. If they really wanted to see their grandchild they would make the effort.

Why are you having to facilitate a relationship between your baby and your ex's parents? It's up to your ex to take the baby to see his parents. You're not stopping your ex's parents from visiting their grandchild in your home (which is generous of you). Where is your boyfriend living? By himself or back with his parents.

Expecting you to travel 50 minutes on a train, with a 4 month old baby and all the things you will need to take with you, is ridiculous.

Are you breastfeeding, meaning it's difficult for your ex's parents to see the baby without you being there? Unfortunately, that goes part and parcel, with having a very young baby, and can't be helped. For the time being, until the baby is older, they may need to accept that you need to be there, and that means they see the baby at your home. Not all babies will actively take a bottle, even with expressed milk (my son refused!), so it may not be possible to give your ex milk to feed the baby.

After their character assassination of you I’d have nothing to do with them at all. They wouldn’t be welcome in my home or within sight of my baby.

You’ve got enough problems with a useless addict ex, save yourself from further stress by blocking his mum and tell him you’re not facilitating a relationship between them and your baby.

It’s great you’ve got a supportive family of your own. Well done for properly splitting up with this unpleasant lump. Keep remembering his family aren’t your problem. You owe them nothing and given their criticisms of you and your parenting they’re of no value at all to your baby.

Fuck no. Baby isn’t a teddy and doesn’t need socialising until like 3.

Definitely start a text trail about his addiction issues with him, confirming that you are not allowing him to have the baby on his own becauseof this.
Get screenshots of these.
They may be useful.
Tell your GP of his addiction issues, so they are noted.

This is his family.
Nothing to do with you.
Do not allow them to visit YOUR home.

Arrange a public meeting place, life a coffee shop.
They are a joke wanting you to travel by train.

Stop listening to him about his families views about you.

YOU are not the one with addiction issues.
The cheek of him!

Grandparents have no legal rights. And no, I wouldn't be travelling a 2 hr roundtrip to see randomers just because they're connected to my ex.

Yep, agreed just do what makes you happy!

HIS family members think you're unreasonable - that's the family members of the drug addict and the lazy entitled grandparents
Just tell him his family members are as high as he is and if his parents can't be bothered to come to you they can do one
Put your baby and yourself first - you are doing great

I’d probably block them all and give ex limited time to yourself and little one. You do not owe any of them anything.

Not your problem. If they want to see the baby, then Dad can take him, or they can visit when Baby is at Dads. Not your responsibility.