Been discussed on here before, it's superb, I watched a couple of nights ago for about the hundreth time. What speaks volumes is it being a good film in general not just good for a zombie film, you could enjoy it even if zombies aren't your thing.
The sequeul is available to watch on Sky Movies as well (Peninsula) which is alright but it really doesn't compare well to the standard set by Train To Busan.
Also if you haven't seen it, All Of Us Are Dead on Netflix is a South Korean zombie series, one of the best things I've watched on there.