Question Author
Thanks for everyone's responses, sorry I haven't been back on the site recently, been away on holiday.
To answer some of your questions, my father in law was divorced from his ex wife, so she wasn't entitled to anything at the time of his death. As far as I am aware, each sibling got something of their father's when he died.A few years later a rift developed, and my husband's brother and sister fell out with my husband and his other sister,it has only been recently that the brother has shown any interest in the "record collection" ( I believ e because he is now unemployed and desperate for money). The collection did exist,but we have no idea of it's value, it has now gone to a charity shop anyway!.
The solicitor's letter is genuine (they have a website),however,you can tell by the tone that the brother doesn't have a leg to stand on!