Are all US video releases of this British giallo complete? Is there a preferable release I should look out for?

The UK video release is sadly the heavily cut BBFC "X" cinema version which loses the entire pre-credits sequence.

Night, After Night, After Night. (UK video)[/I]

Not that it' answers your querry, but I picked up the Sinister release of this one a few years ago and it's complete from what I know, and is still available. It's a bit dark in some night scenes buit otherwise doesn't look too bad.
I never caught up with any of the other VHS issues ( Monterey, Unicorn ect ).