I know you are doing this as a present so is this what you now know?
Your grandfather John Baden Powell, born 1901, died 24 October 1956 according to the probate calendars
(If you have a subscription to Ancestry, you can see the record - go to the card catalogue, type in England probate and then put John Baden Pwell in the names boxes. Scroll down till you find the record in 1956)
You can buy a copy of his death certificate from
www.gro.gov.uk for £9.25 with this reference
Dec 1956
POWELL, John B, aged 54, Durham E. 1a 344
but you won't necessarily learn much from this cert apart from the cause of death.
This could be his birth
Mar 1901
Powell, John Baden, Sunderland 10a 661
Your grandmother Edith Annie Evans, born 20 April 1901, you have her birth cert. Parents Robert & Frances. It looks like her family came from Wales and moved to Durham a few years before she was born.
married John Baden Powell in 1931 and became Edith Annie (or Edith Hannah) Powell
Mar 1931
Powell, John B, spouse Evans, Sunderland 10a 896
Evans , Edith H, spouse Powell, Sunderland 10a 896
She died in 1976, she may not have left a will. You can check here
https://www.gov.uk/search-will-probateI checked for Alan Evans Powell, he died 28 September 2011 and left a will. It's quite recent so someone in the family should have a copy you can have a look at.