Do any 'officials' check such events as this?

No. Prior discussion with County Archaeos is something that ought to happen IMO but doesn't.

PAS Finds Officers attend some, if invited, but only to record stuff that's shown to them. They have no veto or supervisory function.

There are often "Dealers" in attendance, with their own tents. Nice. Out of the field and onto Ebay within hours, very efficient.