I've just had the problem you originally described. So I simply forwarded the rejection email, which had the original suspect email attached as an Outlook item, to phishing@bt.com. It worked this time. I got an auto-reply saying Thank you for contacting the BT Trust & Safety Centre. Timely alerts from our customers help us to act quickly and protect many more people from being affected.
Glad that you have had success Hughieg. My address must have been circulated pretty widely so I now receive multiple mails daily and have decided to label them all Junk and let the filter deal with them, so far it seems to be working.