The Blu-ray of the 1981 mini series looks excellent in comparison with the previous DVD. I believe I saw the 1960's movie on TV 30+ years ago & was unimpressed. The 2009 mini series is fun but difficult to find streaming & expensive on Blu-ray.
The Day of the Triffids (John Wyndham, 1951) is an iconic sci-fi novel. I read this years ago, and it's a great post-apocalyptic story & a very disturbing premise - i.e., plants taking over the world.
And, this 1981 BBC mini-series is by the far the best adaptation of the novel. It's relatively long; has a lot of detail & scenes; and, some of the dialogue is taken straight out of the novel. I did see this on DVD years ago.
Hopefully this will be released on Region 1 Blu-ray at some point. I don't have a Region-free player, so have no way to play the current Blu-ray out there.