I have a child in mainstream school who suffers with autism, and although I'm unable to diagnose your son, it's possible that with his good communication levels he has Asperger's Syndrome. These conditions can be difficult and lengthy to diagnose properly, but you need to start by being referred to a paediatrician who can then arrange the appropriate tests.
If you're in the UK, I assume that you mean by a 30 hour 1-2-1 statement for school that he undergoes an ILP (individual learning plan) and has 1-2-1 help? This is a lot. If he's actually been "Statemented", then his medical condition should be down, and I don't think this'll be altered.
The presence of ADHD is detected by tests run by your paediatrician, and can be coupled with various other conditions, such as autism, dyspraxia & Aspbergers. I personally refused to allow my son to have medication such as Ritalin, after researching the long-term effects which it can have, but many parents - and children - seem to find it of benefit. Ask your GP for a second opinion,and asked to be referred back to a different paediatrician. My own son's come on in leaps and bounds - far more than anyone ever hoped for, so best of luck with it.