If you all are looking for accurate HP figures, there are some options on the way.
Knight miniatures is coming out with a Harry Potter miniatures game. If it's similar to their other games (They make the Batman and other DC miniatures games) the figures should be very close to 1/48. Knight models are typically what is known as 35mm (sole to eyeline measurement of an average human). That is right around 1/43 scale, Should be out soon.
Their page for the game is here. Not much there yet but a bunch of pictures of the figs painted up areA. They look dang good which is no surprise from Knight models. The figs will be nicely cast in metal and top notch quality but they'll also likely be 7-12 bucks each.
Very nice figures. How many characters in total?
Sean
The link shows 10 so far, but that's just the initial offerings. Most games launch with a small selection and grow from there and this will likely be no different. There will probably even be different sculpts of major charachters over the various releases. I personally wouldn't mind some more sedate and less in-the-wind versions of the main charachters.
Those figures you posted look good but the link you have says they are 28 mm high and unpainted you have to paint them. An average O scale figure is around 50 mm high!
A bit of confusion there. In current wargaming parlance, "28mm" is a catch-all term for most wargaming minis that range from 28-35mm in height (measured from sole of foot to eyeline). The size range seems to get bigger every time a new figure comes out, a phenomenon we refer to as "Scale Creep".
I don't think Knight has officially named a scale but their previous models were some of the largest in the industry, being around 35mm from sole to eye which is about 1/43.
I will defer to you about O scale figure height, but 50mm seems shockingly tall. A figure that is 50mm high is probably about 48mm to the eyeline, which would make it somewhere between 1/32 and 1/35. That's considerably larger than O gauge which I've understood to be either 1/43 or 1/48.
You would definitley have to paint them or pay to have them painted if you didn't want them all to be sliver-grey.
For more about the vagaries of scale and how millimeter and fractional scales are calculated, there's a very handy document at The Miniatures Page .