From: Colin Forrester 
Newsgroups: uk.finance
Subject: Re: Standing order - Banks passing personal details to other banks
 - Can they do this
Date: Thu, 28 Sep 2006 10:57:31 +0100

ajja@btinternet.com wrote:
> I have just spoken with my Building Society and they have had no
> contact from my friend's bank whatsoever.
> 
> The letter has come direct from his bank, dated the 25th and was
> recieved on the 27th.  It is interesting that it was addressed to me on
> the envelope, but the letter is to me C/o the building society.  There
> is no way that it got to my Building Society on Tuesday and was posted
> out the same day especially as they have confirmed that they have not
> had any contact from anyone other than myself regarding this issue.
> 
> I have a call into the person that wrote the letter, and I am waiting
> him to return it.

Have you considered that your friend may have disclosed your address to 
the bank?