Your post doesn't actually ask us to provide any specific information or advice, so I'm not entirely sure how to respond to it.
However if the council officials send their letter to your current address (rather to your husband's one), and you then to respond to it, they've automatically got some proof of where you're currently living.
I suggest filling in any form(s) they ask you to complete but also sending a covering letter, stating:
(a) when you moved out of your former shared home ;
(b) when you moved to your current address (if different) ;
(c) that you've not co-habited with your husband since the above date(s) ;
(d) that you're registerd on the electoral roll at your current address ;
(e) that you pay Council Tax to Blogsborough District Council (quoting the reference number on your Council Tax forms, if possible) ; and
(f) that you're willing to provide any additional evidence as proof of your current address (such as utility bills) upon request.
That should hopefully convince them that they're not only barking up the wrong tree but in the wrong forest.