GC, a friend in a similar position to you was having problems with Catalogue companies. The previous tenant of her flat must have ordered a load of gear before she did a bunk.
After sending the letters back for months she eventually received letters from court which she returned, this time with a covering letter including a copy of her tenancy agreement which proved that the 3rd party debts had been prior to her living at that address.
I'm not sure how you would feel about sending copies of your tenancy agreement out to these firms but it may be another way forward.
Unfortunately as far as I am aware, the
Mail Preference Service would not stop this kind of post. I'm registered and although I no longer get post from Direct Mail companies I have noticed that the amount of flyers delivered by my postman has more than made up for the shortfall. LOL...not.