Well, that should have been good.
It starts off during the time of the first film, with another party of survivors holed up and hoping the food will last. Inevitably, the Infected (who are not yet starving to death) find them.
First irritation: the jerky jump-cut photography is effective when done well. But when it's so jerky and so jumpy that you can't tell where we are, who is killing whom and so on, it's just annoying. (I found this a problem in Sunshine too.) A shame, because the scene is otherwise a very effective opening, and vital to the plot.
Next, the time has passed, and all the Infected have starved to death. Refugees are being moved back to the UK, and kept in some luxury in a military-protected complex on the Isle of Dogs in London. Why London, you may ask? Why indeed. As they acknowledge, there are still a lot of unburied bodies, loads of disease, and (as they don't acknowledge) a lot of surrounding buildings which would make it very hard to hunt down the Infected, should another outbreak occur.
The first half hour or so is very suspenseful. You know there's going to be another outbreak, because if there wasn't there wouldn't be a film. You get time to care about the characters so that you hope there won't be another outbreak, even though you know there will be one.
When it does happen, it creeps up on you gradually. [Really spoilery now - look away if you don't want to know.] They find someone in London who is Infected inasmuch as she is carrying the virus, but she is showing no symptoms. An intriguing idea, I thought - one worth exploring, but it doesn't really happen.
And here's the first idiot-plot point. They take her to a hospital room in the heart of the complex, close to the main population. Despite the presence of guards all over the place, they do not think to monitor her - not even when they realise she is carrying the virus. Inevitably she passes it on.
Now the military are prepared for the possibility of a second outbreak. They have holding areas to which the civilians must be taken. Sounds good, right? Holding areas where they are perfectly safe until the crisis has been dealt with, right?
Well, remember that Simpsons episode with the rhinocerous? They are able to "secure" it by putting it behind some flimsy chainlink fencing and locking the gate with a piece of bent wire. And that's fine, because The Simpsons is a comedy. 28 Weeks Later is not.
So, the civilians are herded into this big room with swing doors at either end that might as well have been tied shut with string. And then the lights are put out for no apparent reason.
After this piece of sheer stupidity (on the part of the writers), all hell breaks loose. After that it is typical Hollywood - expendable characters to be expended at regular intervals, and a sequence of action scenes.
All in all, fairly engaging and entertaining, and very tense in parts, but all the good stuff is in the first half. Not up to the standard of the original, which was something special. (Yes, it was a rip-off of the Romero Dead movies, but it did it with a style that made it its own thing.)