Citizenship through Grandfather

Hi all! I'm currently looking at trying to obtain some form of Polish citizenship, as my Grandad was Polish. It's proving a bit difficult, as he passed away before I was born and didn't share much about his home country, so my Mum only has tidbits of information. She kept some of his documents, which is all I have to work with. She's going to double-check to see if she has anything else, but it's looking unlikely. Any advice would be very welcome, so thank you in advance <3

Great-Grandparents:

• Date married: unknown
• Date divorced: unknown

GGM:

• Date, place of birth: unknown
• Ethnicity and religion: Roman Catholic
• Occupation: unknown
• Allegiance and dates of military service: none
• Date, destination for emigration: N/A
• Date naturalized: N/A

GGF:

• Date, place of birth: unknown
• Ethnicity and religion: Roman Catholic
• Occupation: Farmer
• Allegiance and dates of military service: none
• Date, destination for emigration: none
• Date naturalized: N/A

Grandparent:

• Sex: Male 
• Date, place of birth: 10^(th) October 1928, Dabri, Czernelica, Poland
  • Apparently, this area is now part of Ukraine, which may complicate things?
  • My Mum also says that my Grandfather’s birth certificate was destroyed in a fire. I’m trying to track a copy down, but it’s proving difficult, so if anyone has any advice on this, I’d really appreciate it.
• Date married: 13^(th) September 1958
• Citizenship of spouse: British (never claimed Polish)
• Occupation: Sugar Processor (in England, he lied about his age and went straight into the military as a teenager)
• Allegiance and dates of military service: served as part of the Polish Armed Forces with the British Armed Forces but was discharged by the Polish Resettlement Corps on 9^(th) March 1948 after 1 year 137 days service. 
  • I believe from this point onwards, he lived in England.
• Date, destination for emigration: unsure exact date, roughly March 1948, based on the above, England
• Date naturalized: 13^(th) March 1959

Parent:

• Sex: Female
• Date, place of birth: January 1964, England
• Date married: August 1998-ish
• Date divorced: N/A

You:

·       Date, place of birth: October 2002, England

Documents I have so far:

• Grandfather’s certificate of Termination of Services from the Polish Armed Forces, stamped and signed, saying he served for Poland. 
• Grandfather’s discharge papers confirming date of discharge and length of service. 
• Grandfather’s death certificate (from England)
• Grandfather’s certificate of British naturalisation, stating his place and date of birth, nationality (as Polish) and name and nationality of my Great Grandparents (as Polish)
• Grandparents’ marriage certificate
• Less relevant to this, but a document authorising him to wear the Monte Cassino Memorial Cross, in Polish. 
• Also, less relevant to this, but a document acknowledging that he was part of the 3rd Carpathian Rifle Division.