This is the distribution of the 3 main variants of the IS/IZ/IZZard at the 1891 census. As you can see it is mainly a south of England name and remains so to this day



                                                                                                                 Click on thumbnail for full size picture


There are also all variants of the name in Australia, Canada and many in the USA, there are some in Scotland who stem from the Bromley Isards.

I have not found any yet in New Zealand or South Africa.