I don't know much about England¹, but in Scotland a 2001 Sheriff Court case Kinnaird v. Higson, is a modern instance in which the court held that the mere fact that bad language has been used towards a police officer does not, of itself, justify a conviction for breach of the peace (a broadly defined common law offence, as the various public order acts don't run in Scotland). There is now a substantial line of authority from this case.

1] Although I believe that in England&Wales, Nawrot and Shaler v DPP 1987 took a similar line, in the High Court.