I find it varies from airfield to airfield. Sometimes the flight guides will specify "PPR from ops on telephone number XXX", which leaves no room for doubt, other places are less clear.
However, I'd suggest that it's not really worth worrying about. It's always a good idea to call the airfield before you leave, to check that they're open, there are no special events on, etc, whether it's PPR or not.
I can think of twice within the last year when I've changed my plans after calling my planned destination, both at fields which don't require PPR. Once was a fly-in - the airfield was open, although they preferred not to have arrivals from anyone not connected with the fly-in during the time when I'd planned to arrive. (Would have been better if the event had been NOTAMed, but it wasn't.) The other time, when I called the airfield they told me they were closed because the runway was covered in snow. I went for a local flight instead, and heard at least 4 aircraft on the local LARS frequency reporting that they were heading to the airfield in question. No doubt they all found somewhere else to go for lunch instead.
FFF
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