I don't know if this has already been brought to everyone's attention, but both VM and BT are members of the ISPA:
http://www.ispa.org.uk/
All ISPA members are
Obliged to conform to a code of practice.
The ISPA code of practice is here:
http://www.ispa.org.uk/about_us/page_16.html
The complaints page is, of course, here:
http://www.ispa.org.uk/complaints/