Thanks for all of your advice everyone... LOL its a lot to take in!
TBH I haven't been hugely concerned about it, as I have convinced myself that he will develop at his own pace. But more the comments from DP, and knowing there are other kids much more advanced than him has got me thinking...

Thanks for the information Kelly... He can do everything on the 18 month milestone list (except he doesnt say no - he will shake his head no though)
And on the 24 month milstone list I have answered no to #'s 1, 2, 4 and 6.
Hmmm.... I think I will make an appt with my CHN to get his hearing tested, and to see what she thinks.
I don't really know what to think now?

In the meantime I will be using your suggestions Jillian, they sound great... thanks for that!