Please excuse two posts in one day, but I am so happy someone else has finally noticed this, albeit somewhat late:
"The first 45 minutes of 28 Days Later are the first three chapters of The Day of the Triffids, marginally modified with the addition of zombies."
http://news.bbc.co.uk/1/hi/magazine/7762438.stm Triffids is my favourite book and I felt really frustrated that it wasn't acknowledged or credited in 28 Days Later (plagiarism much?).