Action Fraud has just replied to Tracey Cosford's report and this is what they have said:
Action Fraud Hi Tracey, I’m sorry to see that you have received this email. This is a very common scam email which if responded to, you are asked to pay the amount of money shown on the email to keep these apparent videos/pictures from being leaked. If you have not responded to this in any way, you can forward it onto our phishing email address which is: NFIBPhishing@city-of-london.pnn.police.uk . Kind regards, Shannon (Action Fraud Advisor)