I started with all possible good intentions: it was a BBC production and I am a fan of Doctor Who and even Torchwood; I have seen the original Day of the Triffids and I liked it (even if I thought the premise to be pretty hard to believe) and I was prepared to enjoy it as a holiday release, with not much substance in it.
This being said, I really enjoyed the start, even if clearly beset with budget issues. I replaced the set in my mind and went on. The premise was a bit ridiculous, but that was in the book, so OK. Then Joely Richardson entered the scene and it all went bad. I have seen her in other movies and she was a decent actress. So either my memory plays tricks on me or the director messed it up. Badly! All her lines were out of place, her behavior like taken from a blond girl joke and her acting appalling. Eddie Izzard did a decent role as the psychopath trying to take over London, the rest of the stars just played average and mostly pointless roles, roles which could have been played by any other actor.
The ending was a chaos of irrational behavior, bad acting, predictability and pointless narration supposed to "open our eyes". The ending really messed things up, both from the standpoint of character development and end feeling.
Bottom line: decent effort, but ultimately a failed one.