In 1946, Winston Churchill gave the Iron Curtain speech that created the ideological framework of post-war central europe. In 1948, Clement Atlee enthusiastically led Britain to be the primary recipient of the Marshall Plan, alongside France and West Germany. In 1949, joined NATO in an alliance with other European powers. Despite De Gaulle vetoing the UK's application to the European Economic Community multiple times in the 60s, Prime Ministers of both the Conservative and Labour parties continued to apply until the UK was eventually allowed to join in 1973.
To me, all of these indicate that the UK had a strong interest, which was robust to domestic politics, in continental European economics and politics. Yet, in 1988 Margaret Thatcher openly expressed distaste towards the European Community, and refused to join the European Exchange Rate Mechanism in 1990. These policies of distancing the UK from European politics seem to contradict decades of foreign policy.
What events in the 1980s made this political change of course possible? Was there any one tipping point? Obviously, this has implications on recent history, which breaks the 20-year-rule, but I'm more interested in the point at which the UK shifted from generally wanting to be involved in the European Community (in the 50s), to generally wanting to distance itself from that same community. What events occasioned the shift?
The answer to this is quite complex but I think the key thing is that the EU changed it's nature and scope in the years between 1973 and 1992.
In 1973 it was still possible to see the EU as primarily a free trade agreement with a bit of free labour movement and agricultural market manipulation thrown in with it.
In 1992 the treaty of Maastricht was signed which, I think it can reasonably said, put in place the foundations of a 'United States of Europe' and made plain that we were now dealing with something a good deal more than 'free trade plus a bit'.
It's impossible to make statements about the sentiment of the British people as a whole about these changes but I think it's fair to say that at least these changes provided fuel for those politicians who had always had reservations about the entire European project.
Throughout that period there were always blocs within the UK who found such strong advantages that they were more than happy with greater and greater integration (manufacturing businesses would be an example due to the greater ease of selling throughout Europe). Conversely there were groups who never had much taste for it in the first place and nothing that happened in those years changed their minds (farmers and fishermen spring to mind).
You'll notice that I've bypassed your references to NATO and the Marshall plan. British people don't really think of NATO and EU as being on the same page, NATO is much less contentious or invasive in their lives and at least until the end of the cold war was broadly looked upon as 'a good thing'. I don't really see the British inclusion in the Marshall plan as being suggestive of a wish to be involved with other European countries, my reading of that is that times were desperate and the money was there - who else got some was incidental.