Oh YG that you have to deal with this crap.
My mum had something similiar this week. She has a small endowment policy due to pay out in the new year. It was originally in joint names with my dad. Every year they have written to 'Mr XX (deceased)' with details of the policy. The most recent letter asks for his signature before they will pay out .
He died in 1999.
Stupid gits.