That's great - sounds like you are really on top of things already!
We actually saw Margaret O'Driscoll when my DS was 15 months old, when I first started having concerns. I thought she was lovely - very kind and very switched-on. She said that there were red flags but that he was too young to diagnose at that age (which I think is what any paediatrician would say) and that she would like to see him again when he was 18 months old. We ended up going to Daphne Keene in the end though simply because I had read so many positive reviews of her on here. But I would have been happy to go back to Dr O'Driscoll too.
I haven't heard of Stefan Studnik but it's always a good thing if they do NHS work as well as private, as I have heard some local authorities can be funny about accepting diagnoses from purely private doctors.
Re pre-schools I am not sure - Daphne Keen thought it would be good for our DS to go to a specialist pre-school, but now that we have the ABA in place I think we will hold off for another year because I think the ABA programme will be more effective. Also, our ABA consultant thinks it's best if our DS attends a mainstream pre-school/school (with an assistant if necessary) rather than a specialist school - her view is that children who are severely autistic need a specialist school but if there are no real behavioural problems and communication problems are not too severe then children can really benefit from being in an NT environment. So we are going to sit tight for a year and then see whereabouts on the spectrum DS is looking like being and make a decision from there.
Our DS also goes to our local early years centre which has two two-hour small group sessions for children with autism/other delays - a bit like a special nursery, but the parent/carer stays - so you could see if yours does the same thing?
I do think one-on-one teaching is quite important, especially at this age - but whether or not this will be possible for you (and whether pre-school would be better) will I guess depend a lot on your current childcare arrangements and what position you are in financially. Do you look after your DS in the week? If so, you could really throw yourself into learning the ABA/More than Words/SALT techniques and make a tremendous difference just doing that. Or you could put a proper ABA programme in place (but this is enormously expensive).
What we are doing is having an experienced ABA supervisor come and work with DS and train our nanny for 10 hours per week and then our nanny is doing the rest (me and DH are also learning so we can do it on weekends). We're also making lots of time for playgroups, playdates and activities and things as well so that he does get some interaction with other children.
I think adrianna22 hit the nail on the head when she said that it is not so much about just having an hour's SALT or an hour's Portage or whatever per week - it is about you and whoever else looks after your DS completely immersing themselves in the techniques and doing them all the time, day in, day out.
In terms of SALTs, the one we saw privately was dreadful (the NHS one was better, although we only got one hour every six weeks
?) but I remember reading a glowing review on here by the mother of an autistic child for The Children's Place on Harley Street so you might Google them? The key is to find one who specialises/has lots of experience in autism - because VeraGrant's post is unfortunately reflective of the experience quite a few parents have (including us).
Ooh, in fact, my ABA supervisor mentioned that she knows an excellent SALT in London looking for more work - apparently he is free on Saturday mornings. I can find out details for you if you like? I think she said he was about £50 per hour.