could he be on autistic spectrum?

My son is 4 and just started school in uk. He can read very well, write and spell using his phonic knowledge. From a few months old I noticed his eye contact wasnt right and he also has a milk allergy.  He is so polite, will share and is affectionate. He can read expressions and understands tone in voices. He's not so good with social skills and his conversation skills aren't in line with everything else he can do. He talked,knew alphabet and could count to 20 at 2.  When trying to hit or catch a ball his gaze is odd. He can ride a 2 wheeled bike.  
His cousin of the same age doesnt even know the alphabet yet, but talks in great detail about what shes done, seen etc.  Its so noticable to me when they are together.  He plays along side others and isnt fazed by large groups or noise, but he will go off and play on his own, which he often prefers to do. He responds better to other children when he's outside playing.  He talks a lot about "it's only pretend" and will ask a stranger with a dog, why have you got a dog?

His nursery teacher had the special needs co ordinator observe him a few times but he was ok with things she saw and with things she asked him to do, like 3 step request.  He is very easily distracted.
He picks things up so easily, and even uses google to find what he wants on the computer, but there is something not right.  Ive read page after page on autism and aspergers, but there are areas where its him to a t, and others that aren't.
He does have obsessions with washing machines and vacuum cleaners, lifts and cars, and usually turns his conversations to these topics, or starts them with it too.  He does repeat phrases and script from tv or films, (echolalia) but not to us in a reply, usually in play.  He has an amazing sense of timing and can imitate machine noises.  He's great at accents, but is all this hiding something that no one else seems to see.

Does anyone have any similar experience with their children?