It always frustrates me when so-called health professionals give a time-frame of when children should be talking and even give a percentage of how many words they should be using. I am also not a big fan of HV and the statistics they quote, completely devoid of realisation just how much pressure and angst this puts on us mothers.
I know of several friends whose children, usually boys who seem to always be developmentally slower than girls, who have not said much and then suddenly one day they can't stop. I'm sure that with some children, they are simply processing the information they are receiving and when they are able to, will put it all together and enjoy the power it gives.
Others, will get frustrated at not being able to voice their wishes and you can either use Makaton - the very simple user-friendly sign language, as used by Justin Fletcher on CBeebies. This will give them their own visual language, which will fill the gap until the words come along.
As a final suggestion, you can always get a referral to SALT (Speech & Language Therapy), who are usually very helpful people, in my experience and can usually spot if there are any issues of concern. This is just a suggestion, if you feel it would put your mind at rest.
Good luck and keep us posted! 