Hey. I was in a similar position several years ago. My DS was flagged with ASD traits at 18 months. We got a formal diagnosis at 9. Where we are, I've heard the wait time now is around three years.
Although it took so many years to get a formal diagnosis, his nursery and primary school were pretty good at providing him with support.
These are the things I did. This was some time ago though and I know there have been very serious funding cuts so apologies if some of this is out of date -
I made sure DS was on the radar of as many professionals as possible. Does your DS have speech/language/communication concerns?
My local authority nursery ran free SALT drop ins. I took him along and got a referral. Sometimes a speech and language therapist can help with an ASD referral. They can also write reports which can help with nursery/school applications and DLA.
My DS's nursery took him from two years old - for free - because of his developmental concerns. Have you spoken to the nursery? My DS's nursery had a Senco and she was really helpful - again in supporting our DLA application and also ensuring that DS got support when he moved to primary school.
I applied for DLA. My DS was awarded it from 2 years old - despite having no diagnosis. DLA can be hugely beneficial. You can use it to pay for various therapies for your DS.
Google your council's 'local offer' - this is information about all the services available to families with children with additional needs (some councils are better than others).
Is your GP in the loop? Again, some GPs are better than others. He/she may be prepared to refer your DS to speech and language/OT/physio. The more reports and professionals your DS is know to, the better.
I have two box files of reports for my DS now. All this was hugely helpful for when we applied for his EHCP - which is now in place for secondary.
We did look at going for a private diagnosis at the Lorna Wing center. I think it was going to be a few thousand - they spend the whole day with you and your DC. We decided to wait it out though as he was getting fairly decent support.
Sometimes a NHS appointment crops up from a cancelled appointment so you never know.
Fingers crossed for you and good luck.