Don't know dates, but it did originally air on ITV. I recall watching episodes on Thames, and then later in the week, watching them again on Anglia, which I could just about get,
As in the US, the initial reaction was that it was a masterpeice of broadcasting BUT it took viewers time (some anyway, which is why it initially flopped) to get used to the change in format that we were so used to - that of a single story being contained in just the one episode, HSB's was unlike most other programmes in that you had to actually watch it rather than just have it as background.
It moved to Channel four, who re showed it from the start and showed all the subsequent series. It is actually on TV at the moment on More 4, though it is approaching the end of the run - on the other day was the episode where Joe Coffey was killed.