Court form to obtain documents

[Lentil Chips]

My uncle died intestate. I'm his only relative. For many years he lived with his partner, who we believed was a business rather than romantic partner. The partner's family have all documents relating to my uncle and have changed the details on his car registration with the DVLA. Took advice from a solicitor who told me that everything of my uncle's was now mine. Wrote to partner's family requesting all documents within 14 days or I would take action to obtain docs etc. They have not responded. I now need to take this to court in order to obtain the docs etc. Please can you advise me which form I need to complete to do this? Thanks.