You can go back to archives and pick up things that may look like this was widely discussed, but the archive does not show the big picture....the Anti Common Market League, as you can see by looking at the leaflet was a fringe organisation with little media access. The only serious people who raised the Sovereignty question were Tony Benn, Peter Shore, Michael Foot, and Enoch Powell. Their position was rubbished by 90% of their own Parliamentary party colleagues, and the vast bulk of the media. I don't think there was a single national daily that supported leave other than the Morning Star. Don't forget of course that in those days that newspapers were the main driver...no internet or catch up tv...if you didn't see the half hour debate between Heath and Benn at 10.30 on a Tuesday night that was it...it never saw the light of day again. The main two parties dominated the media to an extent they can't even come close to managing today...all their publications were pro remain and denied the possibilities that fringe groups were suggesting....just to add some perspective at the previous years General Election Labour and the Tories held 96% of the seats.