Actually, this one is a hoax. It's true that companies are making unsolicited calls to domestic telephone lines with recorded messages inviting the recipient to press a key for more information (I have heard one such message myself), but it is apparently not true that you can be charged £20 per minute.

I still wouldn't press a key for more information... just to be on the safe side.

There is more about this at http://www.sophos.com/virusinfo/hoaxes/press9.html