This high risk invasive species has a potential to become widespread and abundant on the property and neighbouring lands and a major pest. As soon as possible I would hand pull seedlings and bag any that have flowers. You can cut and dab with chemical larger plants and this should also be bagged and disposed as general waste. It is likely that a regular eye for new seedlings will need to be kept on the site as there is likely to be seed already in the soil. The good news is that we have a few examples of similar sized infestations in our region where we have had success in control. See Erica lusitanica for further information @Neville of interest to you
Thanks Michael I will pass that on. The property owners actively manage weeds on their property and will give this one top priority. It has only arrived there in the last year or two so they should be able to eradicate it from their property.