The last time I reported someone I got a bollocking from Plod for not doing it sooner…
I was driving on the A19/A168 near Thirsk and a driver flashed me, overtook then slowed down and indicated I should pull over. I did so (thinking there may be a problem with my car) he got out, took a look at me then got back in and drove off at some speed.
At the time I didn’t think that much about it but the next morning I though perhaps I should ring the police just in case it was part of a pattern.
I honestly cannot believe the crap they gave me – saying that it was way too late for them to do anything, that I should have taken his registration plate (as he pulled away I tried to note it but failed), that I should have called them immediately etc etc etc.
So yes – I guess you should call them. But be prepared to get crap from them.