I helped organise a few metal detecting rally in north yorkshire in the mid 00s , Not into the hobby myself but knew a guy who was and wanted to do something for charity. had over 1000 people at the events and met a load of lovely people. if it's land that's not been run before then sure there would be people interested but they aren't going to give away all the find's they'd want a 50/50 split. all the ones i met had a great passion for history but they've all got dreams of that big find that's going to net them thousands. and there are lot's that will just sneak into the fields on a night and do it anyway.