Benefit Advice

I have 25 year old twins who have been diagnosed as having Autism (classic Aspergers) with very slow processing. Since leaving college at 18 they have basically done nothing despite my many efforts to get them out and about.  There has always been on ongoing battle that they are no different to other people their age and there is nothing wrong with them.  We have had several doctor appointments with no help so I paid privately for a mini assessment to get an idea of what their problems were, although I had a fairly good idea what their problem was.  They however believe their problems to be anxiety and inattentive ADHD. The psychologist said they had autism but they didn't believe that and said she was wrong. Fast forward a few years and I have paid privately for an assessment which lasted three hours each. They were diagnosed with autism and very slow processing but they questioned the psychologist and told her she was wrong. So in a nutshell nothing has changed. They are pretty much nocturnal and live in their bedrooms. They avoid going out unless they have to and only with me, they are massively into computers, video games, music, lego and Doctor Who. I am still trying to  change the way they live as one day I won't be here and they need to be able to look after themselves so I have mentioned claiming benefits. They are adamant they don't want to live on benefits and will not claim benefits for autism as they don't have it.  As 25 year olds I can't implement anything on their behalf, I have looked into being their appointee but they have mental capacity, they are actually very intelligent with a high IQ. So what do I do? We all need money to live on and what happens when I am no longer here? They say one day they will hopefully be able to get a job but due to the crippling slow processing (Psychologists words) and their fear of talking to people they never get round to anything. Sorry for the long ramble but wondered if anybody else has found themselves in this situation and what have you done? Any advice gratefully received!