From the BBMF website:
Having survived the War, 'P7' was then sold for scrap to Messrs. John Dale Ltd in 1948 for the princely sum of £25; fortunately the historical significance of the aircraft was recognised and she was generously presented to the RAF museum at Colerne. Restored to flying condition in 1968 for the epic film 'The Battle of Britain', she was presented to the BBMF after filming was completed.