I think everyone has covered most bases here.
Opening someone else email is a crime … but only if it was intentional, and the hard part it proving that.
Regarding Debt Collectors … they have no legal
I’d suggest sending a recorded letter to the Debt Recovery Agency with a few key points:
1) Only the people of your surname live at the property and you opened all your mail, and inadvertently opened one letter addressed to Mr X. (I used to received letters addressed to the “the current tenant/owner” in a bid to get a forwarding address of Mr X).
2) Explain that you do not know Mr X, have never met him and have no recollection of him ever living there.
3) Perhaps include parts of the following:
Please be advised that I will only communicate with you in writing. I have noted your repeated attempts to contact me over the past few weeks and these have been duly logged by time and date. Should it be your intention to arrange a doorstep visit, please be advised that under OFT rules, you can only visit me at my home if you make an appointment and I have no wish to make such an appointment with you.
There is an implied license under English Common Law for people to be able to visit me on my property without express permission; the postman and people asking for directions etc (Armstrong v Sheppard & Short Ltd [1959] 2 QB 384. per Lord Evershed M.R.). Therefore take note that I revoke license under Common Law for you, or your representatives to visit me at my property and, if you do so, you will be liable to damages for a tort of trespass and action will be taken, including but not limited to, police attendance.
Granted that letter is for a debtor to send to the creditor, but likewise you can still point out that you have no business with them, and you do not want a doorstep visit, nor do you wish to continue receiving letters.
HTH