As I wrote earlier, having been flying in UK since the early 1970s, I always make a phone call first, PPR or not.
I've never had someone ask why I phoned, or object to my phone call.
However, a licensed airfield will have published opening hours as part of the terms of the issue of its licence. If the airfield is to be closed during the published hours, a NOTAM must be issued.
Unlicensed..... Again, a phone call helps prevent any embarrassment.