I used to work in law enforcement in Scotland many many years ago (pre the 2016 legislation that Ian has referred to). My rusty recollection supports what Ian Cunningham has said.
PACE doesn’t apply in Scotland, and cases are processed rather differently (though the final outcome in court could be similar). In England if you are going to arrest there needs to be appropriate cause, but you normally do it at the outset of the investigation, and various powers to search etc can be triggered by that action. In Scotland they normally don’t arrest at the outset. You are interviewed and reports gathered, where necessary a search warrant may be obtained, and the case will be discussed with the Procurator Fiscal who will decide whether to take it to court. Once all enquiries are complete and Fiscal's approval given, you are then arrested and charged. That arrest is a specific Scottish legal requirement that brings the investigation to a close, after which the police can’t normally make any further enquiries. In England that would be the point at which you are charged. But that Scottish arrest, usually in a police station, is a very different legal concept to a PACE arrest.
(In Scotland there is a separate power to detain someone, where appropriate, that parallels an English arrest, but that’s a separate story).
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