Thanks to everyone who's replied to this thread. I've had some great advice. I know D's still very young at nearly 3 to be diagnosed with anything but from as soon as he could move, I knew there was something different about him.
We had him in pull up nappies before he was 1 as he couldn't lie still for a nappy change. It was as if we had a goat instead of a child as he constantly climbed on the furniture. He'd climb onto the table & fall off, onto the window ledge & try to get out if we left the window open. Into the oven & the washing machine etc etc..
I feel though as if I'm actually getting somewhere now with him as I'm finally being listened to. I do have a "Bloody Minded Hat", I think I always have had one & I make sure I wear it most of the time. And you're all right, we as parents are the experts when it comes to our children.
From the sound of it though even once he is diagnosed there's still a long slog ahead for us as a family. One that we're more than capable of rising to.