PDD-NOS tends not to be used much in the UK. It's in DSM IV which is the diagnostic standard used in the US, where they seem to be rather in advance of the UK diagnostically (IMO.) In the new proposed DSM 5 things are defined slightly differently. I'm sure that at 2.3 you might struggle to get a DX in this country at all until your DD is older, when rigidity can become more apparant.
My DS2 is 11 and was not noticeably rigid in his behaviour under 3. TBH life isn't that routine and predictable at that age. It was when he started school and routines became more evident that we realised he didn't like changes that didn't go his way. He can still cope really well with huge changes, (including my recent separation and starting secondary school!) so long as he likes the change or doesn't feel threatened by it, but if you change something he likes, ooh, that's a different story!
Like those above, I'd say it's too soon to write off whole chunks of the triad. Every autistic child that I know is so completely different from the others that DXing them with the same disorder at all is hard to fathom until you work out the underlying causes for all the behaviours, and you may find that a lot of the causes are similar. My DS is mainly hypo-sensitive to sensory 'stuff' which means under sensitive. So he likes flapping and jumping, cause and effect toys, noise, movement, flashing lights etc. My friend's DS is mostly hypersensitive, hates noise, can hear lights humming, gets very anxious in busy situations. Chalk and cheese, but a lot of their behaviours are down to the fact that they sense the world differently to NT people, (and very differently to each other.) They have both developed obsessions as they have got older, which is how their need for order and rigidity has manifested itself. My DS has had many obsessions, early ones were playing with my hair and running around a circuit in the house. It has been Doctor Who, now it's a game on his ipod touch. They can last for weeks, months or years.
I have to say that being borderline or difficult to DX is a double edged sword. You have the advantage that your child can 'pass for normal' amongst adults and (sometimes) children, and that perhaps their difficulties aren't so serious, but it can mean getting support is more difficult and that there is a desire to fit into NT society that is difficult to meet.
I'm glad you've found MN SN. It's certainly helped me in the last few months. 