Wyndham's novel was published in 1951, right as science fiction was building momentum through the power of the B-movie. The BBC adaptation naturally updated the original story to place greater emphasis on the use of the triffids as a source of oil (in this case to solve the energy crisis, as opposed to replacing vegetable oil) and genetic engineering plays a greater part in the creation of the triffids as a worldwide plague.
See what they're trying to do here? The plot becomes both an entertaining narrative, and the means through which to discuss the energy crisis and the perils of genetic engineering. This is one of the reasons why I do enjoy sci-fi - it opens an intelligent platform on which to discuss contentious issues of the day. After all, Invasion of the Body Snatchers (1956) was a thinly veiled attack on the perceived threat of Communism, while Attack of the 50 Foot Woman (1958) posited the dangers of women wielding any power of their own. Remember that this came after the men returned home from the war, only to find that the women didn't want to go back to being housewives.
However, I do think it's possible to divide the genre into science fiction, and science fact. The stories that fall into the former are concerned with aliens, outer space, other worlds and so on, whereas the latter deals with the likes of unleashed viruses, killer plants, and so on. Science fact deals with the extended versions of those stories you might read in New Scientist - and it's this element of plausibility which tends to draw me towards these stories, as opposed to those dealing with alien races or ships in outer space. These stories peel back the top layer of 'reality', exposing what lies beneath and providing us space in which to think.
It's funny - the soaps might think that they're representing real life, but it's within the arena of science fiction that we truly see what's going on in the world around us.
What about you? Do you prefer science fiction, or science fact?