In spite of a competent cast and crew, something went wrong somewhere along the line. There are some nice bits in it, but overall it's an anemic vampire comedy. I recall catching this at the drive-in, so viewing it again invokes some slight echoes of nostalgia (when every summer Saturday found a carload of us trying to track down horror films). If you're in the mood, it might make a good double bill with THE VAMPIRE HAPPENING.
The something wrong is mostly the script from Jeremy Lloyd. Much of it sounds like Are You Being Served?, which suggests that David Croft is the one who transformed Lloyd's ideas into something funny. However, Niven walks over several jokes that might have worked with better timing. It almost seems like they wanted to spoof Hammer, but had never seen any of their films.
"Fortunately, Ah keep mah feathers numbered for just such an emergency!"
You're absolutely right...this was trying to spin some laughs off from Hammer's success, mixed in with a nugget tossed to Blaxploitation by featuring a black Vampira. What a mish-mosh of mediocrity. It seemed like it was a couple or script re-writes away from being a passable comedy.
But it certainly had a bevy of Hammer babes in it, sadly, all underutilized and barely even shown!
I'm not really one of those "live and let live" kind of guys...