However someone chooses to look at it, tonyrivers.  There is, of course, nothing official about any of this.  

Personally, I tend to lump it in with the DRACULA films, but it really is not a comfortable fit.  Peter Cushing's Van Helsing is the only obvious connection and, as mentioned in another thread, there is an inconsistency to the vampire mythology.  In HORROR OF DRACULA, Van Helsing flat out states that vampires can't transform into bats, etc.  Then in BRIDES, it's pretty clear that transforming is exactly what Meinster does.

So, while I take it to be part of the Dracula series in most respects, if I'm honest about it, it really feels like a one-off to me.  And a brilliant one.