Wow.... thanks SO much for the responses everyone! Some of the things said have certainly made a lot of sense!

I'm glad the the lining up of things is a normal stage... and he does 'play' with toys, not just line them up, so thats a relief.

They have a free speech pathology service at a uni near me, so I'm going to be putting him on a waiting list, and when the time comes, hopefully we wont need it, but its worthwhile doing in case we do need it.