When has it started from? Nick Berry days when it first started, or somewhere on from that.
Whatever, each episode tends to follow a formulaic formula, and you have a pretty good idea of what is going to happen and when. That said, whilst I have never found it must see TV, it's not a total waste of an hour and can be quite enjoyable. I dhould think a lot of the appeal in the UK though is that it's set in the '60's - music, fashion, cars, attitudes etc etc.
You are close with that. In the Original series, the stories were about a copper and his wife, who was a doctor. Subsequent series still have a police/doctor element and the title refelects this in heart (medical) beat (police).