However in the process of becoming a series, 2/3rds of its cast was replaced, with only the very talented Russell Tovey (as George the wolfman) returning. Another of my favorites, Adrian Lester, appeared in that pilot episode as an antagonist and his role of Herrick, the chief vampire of London, was also recast. (My belief is that if you cast a name actor in a supporting role to help sell your pilot, make sure that role is totally removed from the plot so that people don't expect to see that star again in that role.)
I liked the original actors who played Mitchell the vampire (Guy Flanagan) and Andrea Riseborough as the ghost. So I was a bit trepidatious to hear they would not be returning for the series. For the sake of Toobworld, I began coming up with ideas as to how to splain away the differences in the characters' appearances - maybe Mitchell had cast a glamour so that everyone saw him now as played by Aidan Turner; perhaps "Dead Girl" changed her ectoplasmic shape (and skin coloring) to better reflect her growing, more outgoing, personality. (And that's why Lenora Crichlow assumed the role.)
But I've seen the first episode which aired Saturday night here in the United States, and you know what? I'm not even going to bother putting that much effort into splainins. Instead I'm going to invoke the rule of Occan's Razor.
Granted the general rule of thumb here at Toobworld Central is that whatever is broadcast first belongs in the main TV Universe; so the pilot should have been guaranteed "citizenship", while the resulting series would have been tossed off into the Remake dimension. However, I think this situation calls for a reversal of that mandate in much the same way as "The Incredible World Of Horace Ford" was handled. The original version from 'Studio One' starred Art Carney, but the remake appeared as an episode of 'The Twilgiht Zone' with Pat Hingle - and that's the version most TV viewers know because it's syndicated and shows up still (especially during Fourth of July marathons!)
BBC-America didn't broadcast that pilot, and even though the BBC did, it probably won't see the light of day again (except at YouTube and other online platforms, maybe in a future DVD collection). The body of the series will provide much more to expand the TV Universe than could be gleaned from the pilot only and that gives the series more in its favor for remaining in Earth Prime-Time.
But Toobworld will always be grateful for the service rendered by the pilot episode in first introducing the audience in the Trueniverse to these characters.....