I've been onto the local (Stafford) a couple of times. Asked staff if it was ok as I arrived and they were fine about it, just asked me to keep a face covering on which I obviously complied with.
I've also seen 3 other spotters on there when I walked past today (2 of whom are regulars and always travel by train). On top of that I've heard of people spending hours at Doncaster (one person reported spending 8 hours there and was one of many spotters at the end of the usual platforms) and also York seems to have become a bit busier with spotters recently (judging by activity on the railcams) and it will be interesting to see how busy York becomes tomorrow as Tornado is due to pass.
Equally, there has been a noticeable increase in photos taken at lots of station locations - big and small, staffed and unstaffed so I don't think you'll find many problems (the only places people are reporting issues is stations in London but it seems a few of those have issues with spotters anyway so that's no surprise). Just be sensible wherever you go, follow the usual guidelines whilst maintaining social distance and make sure you're equipped with a face covering. I'd also probably advise against dashing about the station to get pics and vids from different areas as the more you stay out of the way of regular pax, the less likely you are to draw attention to yourself.