DELETE IT, cath9 and ask yourself why they would send you an email message when they don't have your email address?
It is obviously part of a bulk mailing which uses every combination of letters they can think of, in the hope that by chance some of them will be genuine email addresses. If you respond, they know that they have a hit, and they will continue to ask you questions until they have your bank details.
Then they may SAY that it is to send you a refund, but in reality it is so that they can TAKE money from you.
Go separately to the website of the Inland Revenue, without using any links in the message, and ask them whether they have contacted you. I would bet that they have not.