> You WILL be charged for not giving the PIN to your phone in an investigation. It’s a strict liability offence which means there’s no legal defence.

Again, no, not just "in an investigation".

It has to be an investigation that has reached the point where they have gone to a judge and got permission to serve written notice. The judge will ask them if there is a necessary and proportionate reason. There is then a timeframe in which you have to respond.

Police can't simply demand your PIN and charge you if you don't comply.