I had this one passed on to me as well.
Although it's undoubtedly a scam, a couple of things have been corrupted or misinterpreted somewhere as is often the case with these e-mail warnings.
For a start, this version gives the number to call as 0306 6611911. There are no 03 numbers in use at present. The version I received gave the number as 0906 6611911, which is indeed a premium-rate number.
Assuming it's valid (I'm not calling it to find out!), the standard BT billing rate for that number would be £1.50 per minute. So it's not quite the case that you'd be charged £15 as soon as you're connected, but of course if they can keep you believing the scam and hanging on for 10 minutes........
