I'm not sure how much you know about the UK schools system. It will also depend on what part of the UK you're talking about: England, Scotland, Wales and N.Ireland have different rules around schools/SEN/applications etc. I only have experience of the English schools system.
I'm not sure what you mean when you say you will have to get your DD 'on a waiting list a year ahead'? In England, you apply for a primary school place by the Jan before they start in September. Is that what you mean?
You will also only be able to apply once you have an address in England. (Unless you are part of the armed services or crown personnel.)
Do you know where you're going to be living?
In England, children who have a high level of need/serious barriers to learning, may have something called an EHCP. (Education, health and care plan.) This is a legally binding document that outlines a DC's needs and what the local authority (and school) MUST provide.
If you have an EHCP, it also gives you a greater range of schools (some special schools may insist you have an EHCP).
There's some good info about all this here:
www.ipsea.org.uk/Pages/Category/get-support
All schools in England have what is called a SENCO (special educational needs co-ordinator). Their job is to support DC who have any kind of 'special need'. Some are better than others though, I warn you.
They would definitely be the place to start. You can call up any school and they should tell you who the Senco is - or often it's on a school's website.
In terms of school settings, you don't say what the profile of your DD is. There are also some primary schools that have what's called a DSP or an ARP (designated special provision/autism resourced unit). These are units attached to a mainstream school that specialise in supporting DC with autism. They have highly trained staff and DC spend some of their time there and some in mainstream.
My DS is in one at secondary school. It's not perfect but it's working pretty well for him. My DS will be expected to take some GCSEs but not as many as his peers. He attends most mainstream lessons and is supported at all times by a support worker.
My DS went to a mainstream primary but again he had fulltime support. It worked pretty well for him.
I would say that when you look around schools, ask what sort of support they offer DC with additional needs. How much speech and language they buy in, what sort of support do they have at playtimes for children who are struggling. See what a school's Ofsted report says about the outcomes for their SEN kids. I have found that some 'Outstanding' schools are less good with supporting DS with additional needs as their focus can be on results.
Sorry this has turned out to be an essay!