It's really quite simple (but a bit unethical).
When they ask for Mrs Farren, tell them that you are Mrs Taylor from the Coroner's office and you are there with the police investigating the suspicious death of Mrs Farren. Say that all Mrs Farren's contacts have to come in for questioning and ask for the caller's name and address.
I'll bet money that they don't ring again.........
__________________
Never put off until tomorrow what you can avoid altogether.
The views expressed here are my own and not necessarily those of my family, friends, employer, this site, my neighbours, hairdresser, dentist, GP, next door's dog or anyone else who knows me..