Firstly can I thank all those who have responded.(posted 7599 days ago)To answer other questions that have arisen -
The original mortgage was a joint mortgage with my wife to whom I am still married although there has been no mention of her name on any of the current paperwork and she has not had any contact with either company.
When the first letter arrived I did phone the number but did not admit any acknowledgement of the debt. After the phone call I was on the internet looking to see if I could find information of other such cases and was lucky enough to find this sight so have taken onboard all advice and been very careful in my responses. All letters are now sent by recorded delivery and thanks to the internet I can print out proof of delivery through the Royal Mail's 'Track and Trace' site.