To be a bit annoyed my trip has been hijacked?

Well done going on your own. My ex SIL was like this, she insisted in joining, then she wanted a big variation of plan to suit her wants and ruining it for everyone else ALL THE TIME.

I’m of the idea that if you have a plan and people then want to change it, the best thing is to say “oh, sorry it doesn’t work for you this time, we’ll plan another for another time”. I definitely wouldn’t be ruining my plans because a young person worked late and wanted a lie in… that’s extremely selfish, they would stay on their phones well past midnight regularly but then need to change everyone’s plans because they finished work before midnight??? Ha! If they want to come they adapt to the plan or stay at home.

PS. I’m saying this as a mum of a ND person. We are so accommodating to their needs that it is important to remind ourselves that everyone in the family has the right to be at the front of the queue from time to time, including us, so enjoy your day off without regrets, I’m sure you have earned it!

I agree @Poppyfie1ds.

But would you change your plans to accommodate them?

Joining her - fine.
Insisting she fit in with them - not so fine.

This is a moot point now though as hopefully op has had a lovely day today.

And? It’s still pretty entitled to expect plans to change significantly to accommodate them. I mean, as hard as it sounds the son does need to learn that the world does not revolve around his and his girlfriend‘s preferences. If they can’t make it for the time OP is setting off then they can’t go. SEN or not, if you’re not at the station or the gate at the designated time, then you’re not travelling. Saying no would be a valuable life lesson.

Why don’t people RTFT?

Because they are sooo busy and important and just want to have a go at the OP without the slightest interest in any updates/clarification. and don't care about looking like thoughtless twats

Hope you've had a brilliant day OP, but you'll be relieved to know that there will still be numerous posts telling you what you "should/could" do about the day that has already happened

I still think first post nails it though.

Why don’t people RTFT? The OP has said

‘He isn't a neuroptypical fully independent age appropriate teenager.’
‘He has SEN’

Just say on this occasion im going to go by myself as I want to leave early that you have already made arrangements.. don't let them make you change plans no way.

You just say no. If you must explain, you can say that you’re very happy for people that you love and care for to ‘tag along’ but you’re keeping to your original timings and if they can’t make it, you’re very sorry and will catch up with them at a different time. The operative term is “ tag along.”

A lot of young people can have main character syndrome alongside fear of missing out. This can sometimes make them very entitled and demanding. If DS girlfriend can’t be there at the time you specified, the polite thing for her to do is decline the invitation whether she encourages your son to go along or not is a different matter. Demanding a time change falls into this main character syndrome alongside fear of missing out that they so they struggle to just decline like a normal person.

You deal with this by saying no. A big fat loud no. They’re there at 10:30am (or whatever) or they’re not coming along. This was never touted as a family outing so no need to feel guilty. This was something you were doing that they were welcome to tag along to, if they can’t tag along at the times that you’ll be there tough titty. It’s just a day out and a picnic.

RTFT for goodness sake!

Oh good, infantilising disabled people.

Good for you @HardyPlumEagle . I agree that it's lovely when adult children want to join you for a trip but wanting you to shorten a day out by hours (which is what catching a 2 p.m. train would've done) was too much to ask. It's not as if you were going for the weekend, you only had one day!

I think it's a good lesson for your DS and his GF to learn that if they want to join in with someone else's activity, they need to be prepared to compromise.

Why don't you stick to your plan of having some time to yourself in the morning and just meet up with them later?

This! You can be perfectly lovely and regretful that it won’t work for them this time, but, it’s a no! Reclaim your day.

This - exactly l would be very happy that the young couple wants to join me.

Are they? I'm beginning to wonder 🤔

"not confident with several trains" ??? What age are they, 14??? Get your head out of your arse and tell them when you're going, and if they want to tag along, fine, but don't go changing your plans!!! Jesus wept.

I find this comment shocking.
Surely you must understand that someone might struggle with public transport but be able and entitled to have a relationship?

I’d compromise on a slightly later train, say 10:00, but definitely not an afternoon train. I would pay for GF in these circumstances, but it depends on your finances.

YABU. Your son is a young adult with a girlfriend. It is not your responsibility to get them there. Cut the apron strings.

She’s already explained that she meant the girlfriend’s parents took her son on a trip in their car. The car of the parents driven and owned by the parents.

Also, the OP has had her day out now.

I hope you have a great day out. I'm sorry to hear about your mental health being in a bad place, here's hoping for some better days ahead for you.

Let them take ‘their car’, and give themselves a ‘day’ out that suits them.

I don’t think that is the cowards way out, you have put yourself first and went! Good for you!

Not at all . My adult autistic son has personal relationships which I encourage . Not a GF though , he wouldn't cope with that level of closeness.