It seems that the z-index declared in the css file does not hold, for some reason I can't explain. Therefore it is necessary to declare the z-index for the top image in-line with the html, like this
<div class="cons" id="cons1" style="z-index:3"
onmouseover="if(this.style
.zIndex!=3
)this.styl
e.backgrou
nd='url(fi
nal-shots/
cons2.jpg)
';"
onmouseout="if(this.style.
zIndex!=3)
this.style
.backgroun
d='url(fin
al-shots/c
ons2_Black
.jpg)';"
onclick="promote('cons',1)
;">
</div>
I've tested and put up my results here (I'll take it down immediately you confirm that you're done with it):
http://www.csc.liv.ac.uk/~anthony/temp/indexFINAL.htmlCode attached.