It’s always best for someone to check with the relevant embassy that the death has been reported to them.
I had a friend die in Thailand & six months after his death, his Thai wife asked me to contact his embassy on her behalf with a few pension questions. The death had been reported to the local police & authorities but they never informed his embassy.
You will have trouble finding insurance in the U.K. for 8 months abroad. Most annual travel insurance has a maximum of 180 days out of the U.K. per year and can be tailored to suit your needs but won’t cover you specifically for living outside the U.K.
I have never had to produce an old passport at any bank branch. The passport number will be different but the passport holder’s details remain the same. The bank keeps a copy of your passports on file & are aware that they occasionally expire. I’m not saying don’t take the old one with you but I am saying I have never needed or been asked for the old one.
I have never had any problems at any bank in Thailand because I had a new passport. They simply took a copy of the new passport number, date of issue & expiry and added the details to my account detail…
I have dual citizenship, with passports from both countries & even this never caused any problems…
I have an American neighbour who has a Thai wife & they had a joint bank account with his American pension being paid directly into it.
Her family and friends were always asking her for loans (some were paid back & some weren’t).
Another Thai made an allegation of serious assault against his wife & she was arrested and jailed whilst police investigated the incident and the bank account was frozen for the duration of the investigation & trial, because her name was on the joint account. This meant that he no longer had access to any money from their only Thai bank account, yet his pension was still being paid into it. She was later found not guilty and the bank account was unfrozen again. They now have separate bank accounts and instantly transfer between then as required.