A vampire can learn the language of the victim that they feed upon. In Dracula's case, Harker's blood not only rejuvenates him, but also changes his accent from Romanian to British, and gives him Harker's speech syntax and slang.
In Rules of the beast, Mina mentions a maid in the Rose and Crown. This is a clear reference to Clara Oswald in Dr Who, who worked in this pub in the episode The Snowmen (also written by Steven Moffat).
In the Rules of the Beast, Sister Agatha mentions "a detective friend in London". This is a clear reference to Mark Gatiss and Stephen Moffat's other famous show "Sherlock", in which a detective lives and operates in London.
The scene where a naked Dracula taunts the nuns outside their convent was shot over a period of five days in sub-freezing temperatures. Claes Bang insisted on doing the scene completely nude, much to co-star Dolly Wells' amusement as she was wearing long johns and thermals underneath her nun's outfit.
There was a deliberate attempt in this adaptation to make Dracula's sexuality fluid. (It is intimated in this first episode that he has sex with Jonathan Harker.)