I thought the first season of "Rome" was wonderfully done. So much so that I bought the series on BR. I haven't watched the second (i.e., last) season yet. I have heard it is not as good, but it would be difficult to match the first season.
I was completely engrossed by "Sleeper Cell" when the first season was on. I tried to watch the second season but couldn't get into it. Fortunately, the first season stands well on its own. (It sort of felt like it was intended to be a one season series that did so well that it was extended, not to good effect.)
I believe "Threads" was a mini-series in Britain, but I may be wrong about that as it is only 110 minutes long. It is available on DVD, but only as a Region 2 disc, so you would have to either play it on a region-free DVD player, a DVD-ROM player, or put it on a hard drive and change the region code. I saw it on TV in 1989. I recently found it on Amazon.com and have bought it, but I haven't watched it yet.
"Threads" is about the slow breakdown of social order after a nuclear bomb in England. There isn't razzle dazzle or special effects. I think it is more effective for that reason. I like it better than similar US productions.
The US production of "Life On Mars" ended up being a one-season show, sort of like a mini-series. I understand the British predecessor of the same name was intended to be a one-season mini-series that ended up running two seasons. I prefer the US production of this.
"Traffic" is a US movie based on the 1989 British mini-series "Traffik". (There is also a later three-part mini-series titled "Traffic".) I think the British production is the best of all of these. I think of the US version as being more "cops and bad guys, both with guns" and the British version to be much more reflective of the real issues about drugs.