Spotted a few places where this happens, myself, generally at the bottom of the descent that is to the left of the most northerly of the 2 motorway bridges.
Had to call out the fire brigade, earlier this year, as a smouldering fire had taken hold in the peaty/mossy top layer of the forest floor and we couldn’t extinguish it.
Not sure if confronting people is that practical as they are usually outnumber us and don’t give a fig anyway.
At least we can take comfort from the fact that the onset of winter should curb their activities for a while. The biggest obstacle for several months is going to be dodging the deer, on night rides.
P.S. Do we know each other, @muddylegs