I'm (as far as I know) NT, and have a good friend who is autistic. He's now early 50's and was diagnosed mid-40s. He's highly intelligent but has a number of other physical and mental health problems - I think the correct term is co-morbid conditions, and is currently undergoing PTSD type flashbacks and meltdowns as the result of something which is currently in the process of coming to court (I honestly can't explain in detail but it is not him being sued or anything like that).
We have quite a lot in common. We are both intolerant of small-talk, and both find it hard to understand why people say one thing and then do another (for example, someone says, "I'll call you in the next few days to discuss this" and then a week and a half passes and you've heard nothing), we both have a very dark sense of humour. He is unable to 'filter' much in life - so if we are somewhere noisy he can't tolerate it for any length of time. Same goes for business, bright lights and lots of information - there is just too much stimulation for his to be able to process.
As a result of our friendship I've learned to say what I mean and mean what I say. I keep to the facts, I try my best to weed out unnecessary words and I'll happily back off if he's stressed and struggling rather than keep saying "are you okay? do you need some help?" as that makes him feel worse.
I also have a female friend who has only very recently been diagnosed, in her early 40's as autistic. She is an excellent masker but has anxiety and depression that really kicked in after a couple of tragedies in her personal life. It's only after several years of therapy and counselling that she's realised that she is autistic and is trying to reunderstand herself.
It seems to me that there is a reasonable amount of support available for children and young people (although exactly what will depend, as everything seems to, on the postcode you live in), but for adults, particularly those diagnosed as adults, there is next to nothing.
At the end of that ramble, Toby - do you have other co-existing conditions? I believe dyspraxia, dyslexia and anxiety are quite often associated.