Sometimes when I'm "naming" things, for instance going "Look ds cup....cup" or similar he just doesn't seem that interested in what it's called. An analogy would be it's like me going around a garden with someone pointing out the latin names of the plants, you know I'd just a bit confused as to why they're doing it.
I think this is a very significant point. It's a good analogy, and generally trying to teach the names of things by just repeating their names is best avoided (As is testing them, e.g. Can you point to the cup), because it's not modelling normal speech patterns. So instead it would be: 'where's the cup? Here it is! Mummy's got the cup. Look, she's got the cup on her head. Now it's on your head. Whoops, I've dropped the cup' ad infinitum.
When you say he's not interested, that's significant and it could be that he's switching off.
A bit about me, but I don't want to worry you: my daughter will be 5 soon and is still preverbal. Turned out she had ASD, hence my questions about pointing and joint attention.
BUT your answers to that all sound very positive.
I do think they learn a lot from their peers, so getting him some more contact with other kids his age could be valuable, even if it's just a couple of mornings a week.
And please don't worry about him not talking at pre-school. Any nursery worth its salt should be able to cope with that.
And please please don't let yourself be scared. Honestly, lots of children are late talkers. They really are, and in many cases there is no underlying condition and they catch up.
It's the difficult line you have to walk of not worrying while doing all you can to get him the help he needs. And avaoiding the instinct to jibber jabber - lots of words but making them meaningful. So not just 'cup cup cup' but more like my example above.