Updating after almost a month and a half. I took a break from posting because the constant worry had driven me to some really bad anxiety which I actually ended up starting medication for. I'm doing a LOT better now thankfully.
My son has now been assessed by a private SALT, occupational therapist, and last week by an excellent private development paed as well. All three have now said that he's not ASD, and just seems to have some slight sensory processing issues which are causing his communication delay.
The occupational therapist assessed him at his nursery last week and she said that he doesn't even require any intervention right now and she will see him again in 6 months time to review.
He has made a lot of progress in the last few weeks. He is very engaged, with everyone, brings me toys to play with all the time, and has started communicating his needs. He also said 'shoos' and brought me his shoes to put on for him.
He's making lots of different sounds and seems to be trying to talk and we're sure now that he just needs a bit more time. We're already doing private SALT and I'm spending a lot of time with him and I'm not worried anymore. Apparently his dad (my DH) was also a late talker so could be that as well.
His understanding of language has gotten so much better! He easily understands simple tasks now like 'bring me your shoes' etc, which he didn't a few months ago when I wrote this post. He knows and understand lots of words now and points them out in his picture books. He enjoys doing that now whereas a few months ago he had no interest. He has also calmed down a LOT. He doesn't run around hyperactively anymore and actually sits down and does activities.
So overall things are all going positive and I just wanted to update in case anyone was following this!