Michael Innes's Inspector Appleby novels, DH loves them.
Also there's an author called Chris Crowther who's written four detective novels, all set in the Norfolk Broads. They're all good and you do get some of the 'family background' as the detective - Jack Fellows - is the main character in them all.
Not available in bookshops widely, but he does a very fast and cheap service from his website.
There's another series DH has read, I can't remember them just now, but one is called The Proper Treatment of Blood Stains, so if you google that, it should give you more info.
Happy reading!