Some historical dramas really do play havoc with historical detail in order to make good viewing. This one isn't as bad as some, and the historical back story and fears of the establishment and the population in the aftermath of the Civil War are reasonably welll handled. The hanging-drawing-and-quartering scenes are of course not accurately depicted. That would be extremely difficult to do given the brutality and detail of what is involved in that type of execution, so why bother? What we have is a rather curious invention by the director/writers which is rather horrible but gives a false impression. It would have been better to have the sentences read out in court and leave the rest to the imagination. However, if you want to reflect on the precarious state of Britain post-Civil War, and how this might have led to the supplanting of the Stuart monarchy with what was a Dutch takeover by any other name, then it is an entertaining series peppered with the odd bit of salaciousness.
Rufus Sewell is terrific as Charles II and the series is interesting, absorbing and entertaining. As Big Bob says, the history is not too inaccurate and gives a good idea of what actually went on.