Thanks for your responses Attache and Sirzy
His teacher recommended we get him a sensory chew and I managed to find a really cool one in the shape of a shark tooth.
It arrived yesterday and he loves it. I notice he'll just put it in his mouth and have an absent minded suck when he's thinking about something or watching TV.
He has the steps process for leaving the classroom (put away work, shoes then coat) stuck to his desk at school. I could put something similar in his bedroom I guess.
Thinking about his "quirks"....
He has a really great imagination, comes up with really interesting ideas and loves pretend play. He can be empathetic and show interest in other peoples feelings and motivations.
But....he's also unusually self contained. He doesn't seem to need other peoples company a lot of the time. At school he has one good friend at a time. It can be difficult if the friend moves table or prefers to play with someone else.
His best friendships outside of school are facilitated by me- so generally the kids of my friends.
He goes to a youth club with a lot of kids he was at nursery with and doesn't really interact with them- despite an unbroken acquaintance of 4 years.
The youth club take photos for facebook and you can see other kids making faces and posing for the camera in groups- then photo's of DS just walking about on his own, hiding in his jumper or closely examining a table tennis bat.
I asked him how he goes about making friends and he said that he just plays by himself and if people are interested they ask to join in! Weirdly, I have seen this work for him as kids tend to be interested in his aloofness.
I've also watched him skirt a group of kids for about an hour, playing by himself at a distance and gradually moving closer before feeling comfortable to join in.
He doesn't seem at all distressed to be "left out" btw. He's very at home with his own company and a bit oblivious on playground politics.
He also hates change. For example- he has some babyish posters on his wall which he won't let me change.
He's also odd about new foods, particularly if they don't have a smooth texture.