Of the two referendums that were held in the 1970s on UK EEC membership, the results were amazingly similar.
1972 - 67.7% to 32.3% in favour of joining.
1975 - 67.23% to 32.77% in favour of remaining.
(Yes, there were definitely two!)
But the point I wanted to make with this is that people talk about a referendum in 1975 as if it was entirely our choice.