list of grenadier CoC range?

[Banderium]

How big/small are the human characters anyway? true 25mm?

They are in the 28-31mm range.
I own nearly all of them. In the last two editions of dadi.com, the largest italian convention, there was a guy selling the complete range at the b&b. He bought the stock of stratelibri/nemo miniatures after the bankruptcy of the company. He had a ton of Grenadier/RAFM/Mithril miniatures, all in their original blisters. And they were cheap too! 

[dreamingleopard]

Check out the links here:
http://recipesrealm.com/wiki/index.php?title=Call_of_Cthulhu

You will notice that all the Grenadier figs have been cross-referenced with the new Mirliton codes, too!

[Bossco101]

This might be helpful too:

http://www.miniature-heroes.co.uk/browse/mirliton-miniatures/nightmares-1/page-1.html

[dreamingleopard]

This might be helpful too:

http://www.miniature-heroes.co.uk/browse/mirliton-miniatures/nightmares-1/page-1.html

Not as much - everything that's on your link is on the Lost Minis Wiki, as separate figure entities, cross-referenced with all the Grenadier product codes:
http://recipesrealm.com/wiki/index.php?title=Nightmares_%28Mirliton%29

[Nedo]

The grenadier miniatures now is produced by Mirlinton SG. Nice price for good quality.

http://www.mirliton.it/index.php?cName=nightmares-28mm

[Commander Vyper]

And Doug (E4m) does have a few of the old Grenadier range at an even nicer price! Dimension shamblers, sevitors and nightgaunts to name a few.

[dreamingleopard]

The Lost Minis Wiki has a new address (though for now, the redirect from the old site is working).  Here are the updated pages of interest for this CoC forum:

http://www.miniatures-workshop.com/lostminiswiki/index.php?title=Call_of_Cthulhu
http://www.miniatures-workshop.com/lostminiswiki/index.php?title=Lovecraftian_Mythos_Creations

To see the differences between Grenadier and the other Lovecraftian manufacturers (such as em4, which sells Metal Magic Dunwich Detectives nightgaunts and dimensional shamblers and so on), use the latter link.  Grenadier never made a servitor (Metal Magic made three, which are em4's; and RAFM made the only other servitor).  If you find someone who will sell genuine Grenadiers to you cheaper than your local Mirlition supplier, then your source is either short of space, short of money, short of smarts, or long on niceness to you in particular because genuine Grenadier CoC monsters are worth more on online auctions singly as compared to Mirliton rerelease packs. I doubt Dave falls short.