There has been much discussion of the roles of the French Prosecutor and the French Bureau d'Enquêtes et d'Analyses pour la sécurité de l'aviation civile and whether it was competent for the Prosecutor to pre-empt the air accident investigation. Comment has been made that things are different in the UK.
If this link is correct, there has only ever been one criminal prosecution in the UK of a professional pilot as a result of their actions whilst in command of an aircraft being used for the purposes of commercial air transport and that was in 1991. The incident giving rise to the prosecution was in fact never investigated by the AAIB, but instead by the pilot's employer, British Airways, and the Civil Aviation Authority.
B741, British Airways, London Heathrow UK, 1989 (Legal Process - Flight Crew) - SKYbrary Aviation Safety