So, in 1975 we had the original Survivors, by Terry Nation, in which the devastation is caused by an escaped plague virus. That year also saw the publication of John Rowe Townsend's Noah's Castle, in which hyperinflation is to blame. In a rather more comedic mode there was the first series of The Good Life, where Tom Good's midlife crisis is the principal catalyst for a life of self-reliance.
And we had the TV version of Peter Dickinson's The Changes trilogy (published '68-'70), in which the cause of the trouble turns out to be (and I still remember my feeling of disappointment and betrayal about this when I first read The Weathermonger) Merlin himself, who's awoken in Wales, become addicted to drugs, gone on a bad trip and is flinging spells about to make everyone turn against post-mediaeval machinery. As a child I felt this to be very disrespectful towards Britain's greatest living wizard, but I suppose that that book too was of its time - in this case the late '60s. And I forgave it because so much of its action was set near my own home.
I don't remember whether the TV series of The Changes goes as far as that book. I've just bought the DVD, which begins with the last (but chronologically first) novel, The Devil's Children, and tells us of the beginnings of the troubles. You can get a flavour of it from this trailer. We started watching at my mother's a couple of nights ago, but unfortunately saw only one episode before her DVD player started packing up (we didn't smash it, honest); but on that basis it's just as good as I remember, even if unintentionally hilarious in the way it sets about separating Our Heroine, Nicky, from her father and pregnant mother. As they're hurrying through the chaotic streets to catch a "cart" to the south coast and thence to France, Nicky (who is as affected by the anti-machine madness as anyone else) stops for a moment to attack a Ford Cortina with a spanner, as you do, while her parents go on without her. When they realize she is missing, her father searches for a whole five minutes before deciding to leave her behind in the mayhem. "She's a sensible girl," he assures his wife. "She'll go back to the house and wait. It'll only take a couple of days for me to see you safely to the coast and I'll come back for her." Then next time we see them he's about to put his wife on a boat heading for France, when she has some kind of pregnancy-related pain. A few minutes later we cut back to them again, now both in the boat, and the father is saying, "I'll just see you safely over to France, then sail back, walk to the city, and find Nicky. Now, you're not to worry about her!"
Children were tougher in those days. Luckily, Nicky attaches herself to a Sikh family, who look after her, and then - but I must say no more.
I do recommend the series, though.