Dear Nigel
Thank you very much - in fact I rang them this afternoon, rather expecting them to say they had no idea, and this evening they have come back with the name I was after. I had taken it for granted they would not have any idea, and I'd be needing access to old directories and so on, but not only did they come back with the answer, but they were absolutely charming - couldn't have been kinder. But thank you very much for your offer. Hopefully I can now work out what connection the writer of the letter is to my family.
Again, thanks very much.
Derby Girl