I went back and forth and ultimately started the process twice only to disengage both times.
They're 18 now and doing really well. They had a lot of protective factors primarily because of their personality, family and interests.
It was a risk benefit analysis for for me and it was razor thin. The primary risk for not getting one was although they didn't need support now they may need it in future and it would be much harder to get. I lived (and still live to a lesser extent) in fear I made the wrong choice. I have spoken to them directly about it and they are happy without it at the moment.
Another thing to mention is that, although in retrospect it was glaringly obvious, I didn't see it until they were 11. Once I did I was amazed I was so oblivious. The school tried to get them on the pathway when they were in infants but I thought they were mad.
Currently I feel I made the right choice but I cannot say for sure. I wouldn't offer advice. I think it is top dependent on a number of things.
Not getting a diagnosis seemed to work out well for my child but that is due to a very specific set of circumstances.
Obviously because they don't have a diagnosis I cannot say for sure they have ASD.....but they do... nobody I have spoken to about it has ever raised a doubt. They're fairly textbook.