Hello
I know your grandmother is a very close relative so I'm trying to be extra careful to get it right but forgive me if any of the details of what I found are a bit out.
The one at Bexley does look right - Patricia Anne 26.8.1947 -19.4.2004 Bexley.
So thumbs up to Annette and Carol.
Her birth reg is slightly out Patricia A Johnson Bromley Kent Sep 1946 mothers maiden name Bloom
5B 371 .However her younger sister born 2 years latter is mother's maiden name is Broom.
Her parents married March qtr 1945 Bromley Peter Roy Johnson and Ms Broom.
(I'm not going to her give her mother's full name as it looks like she may still be alive ,as is the sister but her father has died.)
1939 9 Alderwood Road Woolwich
Albert F Johnson DOB 17.8.1892 solicitors enquiry clerk ex Police (actually Albert George Johnson)
Queenie D(oris) 28.8.1899 (nee Mills)
Peter R 7.2.1923 solicitors junior clerk.
Albert George Johnson married Queenie Doris Mills April 1919 St Andrews Plymouth .It was Queenie who was from Plymouth and Albert was from Dartford.
Peter had a twin brother John R Johnson mar qtr 1923 Plymouth. Presumably Queenie went back to Devon for the birth to be close to her mother Margaret ,as she and Albert were living with his family in Kent on the 1921 census.Albert was working for the Metropolitan Police. Queenie's father James came from Goldalming and was a coachman so there are no deep roots in the West Country.
It looks like Peter and his first wife divorced and Peter remarried and there was a family with his second wife. Marriage 14.3.1959 Woolwich to Sheila Ryan 18.5.1934-29.3.2017.
Peter died 3.8.2004 Southend on Sea Dob 7.2.1923 Plymouth.
Hope that helps .I don't want too post too many details in case on mention a living person.
But I think that may point you in the right direction.
Ciderdrinker