There's another scam going the rounds in Britain which involves somebody pretending to be from the HSBC Bank. It's rather more plausible than some of the others and it works like this.

The phone goes, a businesslike voice tells you that she needs to ask you a few non-urgent questions about your account. "First I've got to take you through the security questions. The first half of your postcode is XXXX. Can you tell me what the other half is?"

"On yer bloody bike Missus. My postcode is not one of my security questions."

Useful tip. The chances are that the miscreant party won't have withheld their phone number. This seems to be a useful way of gaining your confidence. If they haven't withheld it, try googling it. If it is a scam, there is a strong likeliehood that you will hit a message board where other people are complaining about the same number.