I think thats fair enough Daz. The sport is run to a gentlemans code and some folk are ungentlemanly. Other than cause the organisers major headaches I think that not shooting with the same person more than once throughout a season would help. I can't see how it could be done easily at national level though.
Other than that I can't think how it could be improved, some people are weasels, some are stand up types. There'll always be someone trying to take the piss to get an advantage. The marshalls are there to over see safety and it's up to individual groups to police the scoring.
I'll have a quiet word if I see something thats I think is cheating in a friendly manner, if it happens again with the same person I'll have a not so quiet word and make sure everyone hears it!
Ryan