Dear Vince,
What a collection! Wow. Some species are a first time for me, seeing healthy examples of well grown plants!
N. pervillei still looks mad about something though... Seems like very few people can make this species happy in cultivation. I'm certainly not one of them either
I realize these aren't your plants, but I noticed some things I'm wondering about. This looks more like
N. burkei to me, than does the plant labeled "N. bukei":

and
While this plant looks like
N. ventricosa, and has been mislabeled at Kew as "N. burkei" for a very long time:
This plant could use a new label, when it was distributed, it widely believed
N. chaniana was
N. pilosa. However, this situation has now been clarified and the other parent of this fairly common natural hybrid is now known to be
N. chaniana with
N. pilosa being much rarer and only known from one location:
N. chaniana * N. veitchii; AFAIK, all plants in cultivation are single male clone.
Not only is this not
N. ventricosa, it doesn't appear to have any
N. ventricosa in it. I swear this looks like what I would expect from a hybrid between
N. eustachya and
N. alata!

and
But it is probably a pure
N. alata (in the broad sense)... Or an example of a hybrid with "hairless alata" species which looks rather intermediate between
N. alata and
N. eustachya. This "hairless alata" (and something else/new again) was featured as
N. alata in Stewart McPherson's new books.
For comparison, here is a photo of pure
N. alata (the plant in the photo is a highlander from Luzon which strictly matches the description by Jebb and Cheek):
I think if you hybridized
N. alata pictured above with the "hairless alata", you would like get pitchers very close to these:
Edited by Dave Evans, 11 November 2009 - 23:15 PM.