It was, but it was subject to the Labour government renegotiating the existing deal to their satisfaction. The new deal was firstly accepted by Parliament and then put to the electorate.
Forgive me I was too young to vote by some distance in 1975 and did not have the political savvy at all aged 10 to have an input in 1975. For 40 years I have been the generation that lived with that decision. Looking at your post I note that
The labour government renegotiated the existing deal to their satisfaction- Cameron didnt. He went for a number of changes and got pretty much squat.
Membership initially was all about trade and a single market. In the late 80s and early 90s that criteria changed and moved towards a federal state of europe and we as a country under governments both Tory and Labour had to renegotiate or veto a number of issues which were deemed unacceptable to our membership. This included membership of the single currency. Even then because of the lack of reform in the 90's a group of MPS formed UKIP initially as a protest against the signing of maastrict. Therefore for 25 years there has been a clear division between the aims to the EU and the willingness of the UK to play by all the rules. No other member has tried to re-negotiate terms of membership to the extent the UK have since joining. As a country we have been a real pain in the arse.
So the referendum was seen as a final put up or shut up by the MPs who supported remain ( 500 out of 650 approximately) and the leaders of the EU who fully expected the UK to vote in and then crawl back under a rock with its tail between its legs and behave itself for the next 25 years. The arrogance beggars believe.
Hindsight is a wonderful gift. I completely agree with DW. A referendum like this is and was always going to be divisive but the vote is an individual one where each vote counts not a first past the post in a region system. Therefore if everyone in Scotland Northern Ireland and Wales had voted in and everyone in England had voted out the result would be out as there are many more votes in England than the other 3 combined.. The motives behind it were not to implement the will of the people it was a control mechanism to get people like Farage to fuck off and allow Cameron to get on with governing while being able to deal effectively with the internal euro sceptics in his party. It was a gamble but a gamble that looked nailed on until about 4am on Friday 24th June.
The culmination of 20 years of poor government policy with regard to infrastructure , housing, NHS education and a 6 year austerity plan on the back of it has led to a huge number of people who were undecided almost tossing a coin. I as a brexiter had to think very carefully about a number of pros. The EU is a bureaucracy but it has done a lot of good things for us as a country.Like many I had to weigh the good with the bad against the current backdrop. I came down in favour of brexit- just. And that is a big difference in the voter. The number of people who voted remain tended to believe about 80% plus in remain. A large number of people who voted leave were 51%-60% in favour so could have been swung either way. The abject failure of senior figures in this country to fail to do that compounds the arrogance of the referendum in the first place. I dont feel I have won anything. I feel that the people have voted and it now sits in a "too tricky tray" for those our votes have charged with running the country and that void will allow extremists to have a voice. A voice that I do not want them to have. Hence why my posts have been about uniting, moving forward and unravelling this ball of string as quickly as possible to provide the stability we so clearly need. My view was that with the EU we needed to be all in or all out with no more tweaks, concessions or changes and that hasn't changed. It appears 17 million thought along similar lines. Maybe if thye remain campaign had done what it was charged with doing we would not have this situation. You will never find a single post from me on here stating I expected to win this. I expected remain to win this but would have been happy knowing I had my say. I do expect however, those voted into power to have plans in place and quickly to deal with the fallout of the result and protect the interests of the country and its people.