Nice BatRep glorius.
Another source of figures you could consider is Irregular miniatures, they do some nice 15mm "star marines" and I'd be tempted to say that their colonial Brits would make a nice 15mm version of the guard regiment whose name has just escaped me - they fought against orks in a "Rorkes Drift" type scenario.
They also do Riot police in their "RIOT" range which could be used as Arbites.
Now you've got me thinking about why we switched to 28mm when 40K first came out - we should have stuck to the 15mm we were using with laserburn!
If I recall there was an article in an early issue of Ragnarok, (magazine of the SFSFW), featuring scratchbuilt Rhinos and Land Raiders in 15mm - looked good too. As the imperial stuff is quite "boxy" it shouldn't be too difficult to scratchbuild form plastic card and makes Apocalypse, Planetfall and Spearhead type games much more feasable in terms of space required as well as cost of raising the forces.
Thanks for the original post Glorious - certainly got me re-examining my 40K and Warhammer projects sat on the back burner.
vT