The NHS ODS Data Search and Export tool holds this information.
Search for your surgery using its ODS code (e.g. X98765)
Expand the General Medical Practitioner section in the results
Each entry shows a GMP code — the middle 6 digits of this code are the PPA ID/DIN
Example: A GMP code of G9999911 is a DIN/PPA ID of 999991
A doctor not appearing under your surgery's record means they are not registered as a partner or salaried GP at that practice. Do not use a GMP/PPA ID that is linked to a different surgery.
"PPA" continues to appear in many places and systems; however, the correct term is Doctor Index Number (DIN). The Prescription Pricing Authority, which gave the old name its initials, was abolished in 2006. The two terms refer to the same identifier.