1. Take the street names of the map of the area you cover and type them into royal mail postcode finder, you will, then be able to do a quick count of the number of houses in that street...repeat until you have done all the streets in your area.
2. Do similar with Zoopla.
3. Visit your local councils website, you can sometimes find out the info you require from there.
4. 2011 census, household statistics.
5. Your local main library should have all the population/numbers of households stats you will need, both present and future.
Local area development plans are usually updated annually and available from library.