Can somone enlighten me regarding 28mm.  I understood 25mm=1inch.  But where did 28mm come from? (prays for a complicated answer rather than missing the obvious )

There was a big difference in 25mm figures when comparing those produced in the early 70s to those from the early 80s.  Certainly more "chunky" and generally taller by the 80s.

Just like action figures of today are invariably musclebound.

As I understand it, 28mm was just a marketing ploy by some minis companies to differentiate a new line from previous ones and other manufacturers by saying, "Hey, it's bigger!"  But at the same time not being big enough to make a potential customer balk at purchasing 28mm because they won't jive with a large collection of 25mm.  They can pretty much be used interchargeably without much consternation over mismatched sizes.  

70's minis were a bit clunky but some have their charm, especially the Heritage Dungeon Dwellers line.  You can just imagine the good ol' days with those minis and a woodgrain box.  Grenadier's gold line series match pretty closely to 1st ed. Monster Manual pics.  And Ral Partha's official AD&D line matches very closely to 2nd ed. pics and are arguably the best sculpts ever done for D&D.  

The plastic stuff is pretty horrid IMO, I won't touch the stuff.

Well, I'm not sure about the whole Games Workshop/Citadel origins of the differentiation, but IIRC, they were the first to jump from 25mm to 28mm and even 30mm in some cases (each size corresponding in scale to 5' height of the figure in game, though all still use 1' or 25mm squares for movement of 5 feet).

Today, most figures are produced in the 28mm or 30mm scale; Reaper, I think, calls it "Heroic" scale. Basically what it means is that if you have older figures that keep to true 25mm, when you use them with modern figs they look like children next to their counterparts. Not as bad as, say, using 15mm figs with 25mm did (I used to use 15mm figs for halflings vs. standard 25mm figs for humans), but it is still jarring. Reaper's "Dancing Girl" figures are as big as some early 25mm Ogres!