Name changed because he's a nosey fucker amongst other things. Happy to be told I'm wrong here.
Without going into the worlds longest story, if you had children with your ex partner, Ex has been with their new partner approx. 3 years and plans to spend at least 2 of his 7 contact nights staying at her house (as well as the children being there at other times also) is it completely unreasonable for me to want to know her address?