Don't know any more, but speak to the Manager at Forest Hill Sorting Office.
I had missing mail over a period of a couple of months some years ago and the Manager there was very helpful, but there's not a lot Royal Mail can do if the post is stolen.
Try to list anything that you expected, bills etc. but it is often difficult to guess what may have gone astray.
You can claim for compensation, but in my case all I got was a dozen first class stamps! Watch out for credit cards that could have got into somebody elses hands.