I think the OP, some posters on the thread, are of the 'Can't go to the loo or get on a train solo' persuasion, though.
I have to say, OP, that this sounds like an incredibly joyless night out, all told, with you planning for earlier trains and trying to get everyone to leave by going for a pre-train wee, and then everyone else going for an unnecessarily long wee, and all that bag-sitting for one another, and then missing the train and presumably you sitting there glowering when someone produced a bottle of wine at midnight, and then sulking and phone calls the next day.
Look, it's miserable that your health is poor, and that you are on a drug regime that negatively effects your social life I've been there and genuinely sympathise but you need to take responsibility for your own arrangements and transport arrangements, and be realistic about how much you can expect even well-intentioned drunk people who are having a good time to act as you have arranged.
I get that your friends presumably had, in advance, every intention of going home on the early train even though that sounds like a very early end to a night out but when it came to it, you came across like the fun police (for good reasons) and they wanted to stay out.
What's happened now, regardless of who is at fault -- is that there's a rift in the group.