As for the user names, the sender will be using his/her own SMTP engine rather than an off-the-shelf mail client, with a programmed element that produces randomised sender names and (purported) source addresses.
As regards your email address, I doubt whether btinternet is to blame... can you be sure that when you check the box for no advertising, your request is honoured?
BTW, the W32 bit refers to the fact that the worm runs on 32-bit Windows systems - that is to say, most worms these days
