This method does work !!
I was sick and tired of receiving sackfuls of advertising mail and unaddressed mail, and only receiving one or two "proper" letters a week.
I wrote to the Royal Mail opt-out, (only for unadressed mail) and duly signed the forms they reckon they require. The opt out people send you a nice letter to inform you that you will also NOT receive Local Authority or Government Information, - to which I told them that that in itself was the best reason i needed ! After six weeks, my incoming mail halved, then mysteriously started again, a couple of months later. On making enquiries, it turned out that the Royal Mail form is only for a period of six months, and they expect you to sign the form EVERY SIX MONTHS ! - - I gave them fair warning, that i had signed one form, and that should I wish to receive adverts etc etc, I would contact them and withdraw it. I also informed them, that from now on, I would save the unadressed mail, and once a month I would post it to their offices.
I did this last week, with an accompanying letter to say this was the first lot, and the next lot was being prepared. Today, I received a letter from them, stating that they had put me back on the opt out, and let my local sorting office know!!
THE SECOND METHOD
Save all unwanted advertising mail, including the pizza leaflets etc etc, - when you receive an advertising letter with a REPLY PAID ENVELOPE, put ALL the mail and pizza leaflets you saved into the reply paid envelope, and post it off.
It took three months, but I DO NOT RECEIVE advertising letters from Insurances, double glazing, gas boilers etc etc etc.
More to follow on THOSE TELEPHONE CALLS FROM ABROAD later.