For agreeing to give my son a lift?

I think it’s one of these situations when you need to look at bigger picture. Your DS has additional needs and will always require some level of support but you can regulate the exact level by teaching him.
I don’t think you do him a favour by agreeing to last minute changes of plan . He has to learn to plan in advance and consider other people.
Also he is 27 so it’s a different stage of life and you have to put his interests first not his Dad’s wishes. Try small steps - don’t change plans but check with DS in advance, advice him to check with his friends in advance and look into supported accommodation option BEFORE having this conversation with DS and his Dad.
And I think you owe your DP an apology, of course changes do happen and he should be understanding but in your case changes became a norm and it’s not right.

OP I understand the issue as I have a 28 year old DD with autism and we live in a place where the bus only comes once an hour if you’re lucky. I do give lifts if I need to but if I’m busy or it will disrupt plans, I just say “sorry I can’t.” And somehow, she survives the disappointment of not being able to do something she wants to do, as we all must from time to time.

You are letting your son down @Starcky

If he has friends, socialises independently and makes his own arrangements then you he can make his arrangements in better time and learn to travel independently.

My 12 yo has ASD and attends specialist school. He travels independently and goes to the shop alone. I’m working up to him making his way to friends independently.

He should have every chance to live as independently as possible.

He needs to be involved in his life and not just a passenger.

His dad has it all at the moment with you doing the fetching and carring.

If your DS at 27 wants to move and could manage let him have a life outside of a village, he'll be closer to you and knows you'll be there if you're needed.

Of course his dad would get to see him, he could get the bus himself into the city for a catch up, he just chooses not to do so, he knows you'll do what's asked of you and in the mean time he's back door controlling when you and your DH get go out and spend time together.

His dad doesn’t work.

Does your DS father claim carers allowance, receive any benefits for having your DS live with him?

In this case I'm also pleased to read that your DH makes up his own mind and doesn't stay home and instead sticks to the plans.

Just seen your update about taxis sorry! Bus service? Could he pay a friend who drives that would be cheaper than a taxi? Get the dad to meet him?
It's not like you don't have to do it ever again, but you're doing all the work - effectively protecting his friendships by sacrificing your own relationship.

I would be frustrated as your DH - it keeps happening with no sign of change. Your DS will never be fully independent if you keep dropping everything for him. It depends on his level of autism but if he is able to go out with his friends, why can't he book a taxi back or something? Surely there are other solutions other than you changing plans and running out to pick him up.

Dad can get a bus to meet him.

Ex Husband can learn to drive, and/or get the bus. Hes being selfish and limiting your sons chance for growth and a social life.

I think it sounds like he is being held back a bit by his father. Moving into central supported accommodation wiuld free up opportunities for him surely? I do think you’d be wise to encourage this as it’ll make it easier. I’d also say sometimes you need to prioritise DH so be proactive. I have plans on Saturday but can drive you on Sunday early in the week so he knows the time you have available as it sounds quite last minute and to ask you as soon as it’s in his diary rather than waiting till day before.

YANBU in giving up your own time to taxi your son around if that is what you want to do. However YABU in changing plans you have already made with others in order to do this. This is understandably causing resentment.
I have an adult DD with ASD who I had a tendency to "baby". She announced she was going to live on her own and I was horrified she wouldn't manage without me. Surprise surprise she is doing mostly fine. I then came to realise that much of what I had been doing for her, while I thought was for her benefit was actually for my own peace of mind (my other DD had been telling me this for some time)
After years of being her taxi, she now only occasionally asks for a lift, when buses or an Uber would be a problem eg transporting quite big things, and manages just fine all the rest of the time.
Obviously with autism being a spectrum your son might not be able to manage this, but if he is able to go out with friends, it must at least be a possibility for him and they might be able to help him out if he encounters any transport difficulties. You maybe at least need to give him a chance to succeed with this.

Didn’t read the whole OP but get the gist. No DP would ever tell me what to do, especially when it comes to my dc. So dp would be out.

I think you need to think about a more practical long term solution to this.
Being 27, stuck over an hour away from any form of social scene and local amenities is going to be more and more isolating for him and limit his opportunities for growth, he is already relying on you to be his permenent taxi service.
Either, he learns to drive (not sure how feasable that is), or transitions to moving out, he comes to live with you, DH moves closer to town, or you budget for transportation.
I don't think long term you are going to do any of you including your son any favours by continuing to be a drop of the hat taxi service for an indefinite term.
What happens 10 or 20 years from now? This needs to be a point where you start thinking about how he can have a life more independantly, how could that look for you all, what do you all need to do to facilitate it. If he needs to live with one of you, then one of you has to move where he can go out and have a life more easily. Or you need to start thinking about how he can live independantly.

I think you need to engage with adult services as your son would like supportive living.
Far better he does that while you are alive, fit and well.
To help him settle.

Focus on what is best for your son, not his father who is thinking only of himself.

Your husband is not wrong to be frustrated.

OP. Imagine you become incapacitated and cannot drive due to medical reasons. What would happen? He would manage. His father would manage. Don't make yourself indispensable. It's not good for you, your partner or your son in the long run.

Is there a reason he lives with Dad, doesn’t seem the most convenient place to live?

Can you give him a 48 or even 72 hour notice rule?

Does your DS have the capacity to say yes to supported living?

He needs to move to the city.
His Dad will have to make arrangements to see him.

@Agixyou say you’re surprised by the comments so far and then your answer is the same as all the others - that the OP and her son are being unreasonable and need to sort other arrangements, even if it upsets the son?

You're not even really enabling your son, who seems quite willing to move somewhere more convenient and to not be so reliant on lifts. You're enabling your ex-husband, who has decided to live in the middle of nowhere with his son when neither of them can drive. I don't drive and I wouldn't live in the countryside and then expect others to give me lifts all the time. I live somewhere with decent public transport. Your son sounds like he has a lot of potential to grow and get more confident in his abilities. The ridiculous living situation is what's holding him back. It isn't your job to paper over the cracks in this arrangement to the detriment of the rest of your family. If your son won't see his dad much after he moves out, that's his dad's fault.

I’m sure he’s not a brat but all children need teaching to consider others, and children with autism even more so. Giving in to his every demand isn’t helping him. He’s clearly able to adjust as you said you didn’t like being texted on the day he needed you, so he swapped to texting the day before. That’s great - carry on explaining and teaching him further.

If he’s getting PIP, he can spend that on a taxi. That’s what it’s for. If he needs support initially to book a taxi, you could help with that. He could also get the hourly bus from where he lives, and then get a taxi once he gets to the town.

YABU because you’re not helping your DS longterm, and because you’re messing your DH round (and your nephew, who’s only young).

My oh and he also does his own shopping. He goes on public transport and goes back on public transport. He lives on the outskirts of a small town. Buses from where he lives are every hour. It takes half an hour to walk into town.

You don't agree to do something for / with someone else when you already have plans. And you certainly don't change the agenda 2000 times to suit the person you didn't make plans with first. I'd be pissed off too if I were your husband.

Your ex cannot hold his adult child hostage at home forever to suit his own needs! Is the ex disabled, is that why he can't get the 2 buses in to town to see DS if he were in supported living?

The supported living sounds a good idea.

What is best for your son?

Tbh in the circumstances I can see why you try to do it as much as possible for him.

I'd probably help my son & skip seeing the ILs & taking a nephew out for the day.

Unless there's only one car & it was either or.