I've given up on F2F social interaction

What is it that you wish to recover from, then?

Although we regard each other as father and daughter, we are not blood related. She is my late wife's youngest child. We have known each other since just before she was 10. That's over 40 years.Her birth father was not a good person. He was off the scene  before she was school age. My late wife and I met during my last and longest psych admission. Although there was a large age difference, and difference in background, it was though we were made for each other. Kismet perhaps.

I've not seen my brother or sister since moving to Wiltshire in September 2017.My brother and I do exchange regular emails. My sister and I? Minimal exchange of emails,or Facebook messages. 

This may sound strange. I'm far more able to say 'I love you' to what I call my 'chosen family' than I ever have been to my birth family. From the age of 8 to 18 2/3s of my time was spent at boarding school. From 1981 onwards, till he died last July, I saw my father about once a year, apart from a 2 week visit to see  him and my step mum in 1995. He chose to accept a posting as British consul general to Atlanta  when I was at my lowest ebb. He then chose to take early retirement and remain in the States, rather than become Ambassador to the Gabon etc.

I saw much more of my mother, but her alcoholism/problem drinking didn't always make for a psychologically healthy relationship.

I hope that your decision works out for you. The only thing that I felt compelled to say is that this doesn't really need to be a final decision. Just what works for now. You have family, and 'chosen' which is so lovely. Was there an element of socialising that led you to having them, though? I'm just saying that it doesn't need to be written off forever and ever and ever.

I'm very much in to minds about friends, they need to be the right people and most of those I meet aren't, I've learned that I'm happier, if sometimes a bit starved of conversation, on my own than surrounded by people I have little in common with. I've spent so much of my life surrounded by people and feeling lonely as hell, wandering round feeling like my own ghost, haunting these social occasions, I never want to do that again.

I actually think that some of us are naturally less social and depndent on others, I enjoy my own company and that of my books, and my garden, I'd like more people to cook for, but thats about it. I have a dog to go on walks with and cats to cuddle, they do sometimes argue back at me, but they're a lot less demanding and hard work that humans. I know it sounds selfish but when I think about whether I want this or that person in my life and how close I want them, I ask myself whats in for me? The answer is often not a lot, I refuse to be the socially needy person anymore who fears rejection and has to mask and pretend to do things I don't like, to pass as a normal human being. I got to exhausted by it all to care anymore, why should I put myself through all that for other people? And that's who I'm doing it for, it was a big realisation to learn that I wasn't doing this for me, so I stopped and I feel much better, more whole and complete, I dont need another to make me whole, or some other romantic carp I am whole and complete within myself.

They primed us for Pole, only for us to retire at the Parade Lap.

Just need to reform society so it is at least accommodating towards us.  Unfortunately sweeping political change takes decades and we are alive now.

I am 42 and was diagnosed at 18.  There's been quite a lot of progress in getting Autism up the agenda in that time but it's quite literally taken half my life for us even to get this far.  I sometimes console myself that a child born today will have it by degrees ever so slightly easier.  I'm not sure if that's true or not.  As for solving my own issues. I don't even know where to start.

Sometimes it's a case of 'Choose your poison'.

I seem to contradict myself on this daily. Sometimes I'm like "I never want a friend again" and other times I'm happy to talk to new people. I know exactly why I'm caught in the middle, but it's largely bad experiences that influence it. 

The tragedy of Autism for many is that humans are not meant to survive in isolation.  Many of us will choose to live that way because of the alternative.  Many of us will convince ourselves we are happy that way for long periods of time.  But because we are human as well as Autistic we will never be truly happy alone and will only slowly become more psychologically damaged by it.