Judges don't tend to press that hard though (the discretion under PACE) which is why it's only when dim JWs try to muck up major child abuse investigations that the stick comes out. Like it did in Newcastle not so long back. And then after months of the judge trying to persuade them to testify of their own accord. They chose to testify on the morning of the trial, rather than spend some time at Her Majesty's pleasure."
Well, yes and and no. Of course, judges can and should rule 'in the public interest'. I am not aware of any case in which a catholic priest (or a CofE priest) has ever been subpoenaed to give evidence of what occurred in a confession, and I would be interested to learn of the procedure which occassioned that. It would seem to me to be covered by PACE (excluded material).
I note your comments that 'Judges don't tend to press that hard'. I'm not sure what you mean by 'the discretion under PACE'. I can tell you that the judges with which I dealt pressed hard, demanded evidenced and reasoned legal arguments, and issued orders/warrants that were never - never -overturned by higher courts.
(This is a UK (E&W) perspective.) Judges don't try to 'persuade' people. They explain the options. You don't f@@k with the judge, ever.
And here is a true story. I had a case (related to my post above about judges ordering bank information). The judge had ordered that material held by the bank (a national) must be produced to us (the police) in 7 days. It wasn't. The local, area, regional managers appeared before the judge to explain the failure. The judge ordered the CEO to appear - and advised that he bring a toothbrush. The material was provided.