while it didn't become the norm for neckwear until post-wwi, the four-in-hand style tie dates back to the beginnings of the industrial revolution as a piece of slightly more practical neckwear for the up and coming bourgiousie. basically, if you have steam trains, a four-in-hand is not technically an anachronism (even if it isn't favored).
X( ... er ... uhm ... i know this because my wife has a degree in theater .. no, really ...
the sneakers can probably be hidden with your paint job. i don't think there's a nike swoosh to shave off ...
* break *
i think the key to making your game mechanism fun is what it takes to kill a zombie. for example, if it's a head shot, which is pretty tough with the weapons at hand, you don't need a big horde of zombies to break the square.
if non-fatal shots slow the zombies movement (by blasting away parts needed for balance/locomotion), then you can get a nice dynamic of "hit and flee" tactics where the brits have to let the zombies get close in order to stop them, then have to reposition before they are overcome. this mechanic becomes more fun if you have wounded or civvies to protect.
another possible mechanic is to limit zombies to movement toward a victim in line of sight (or straight ahead in the absence of a los target). the mindless undead just aren't good at flanking. in that case "hide and seek" becomes viable against a large horde. as well as baiting them into an ambush (remember, they gotta be real close before you can let loose the ambush).
again, with civvies, you might want to have them paralyzed with fear (unable to move) if the zeds have clear line of fire to them. this will require the brit player to split his actions between attacking the zombies and manuevering the civvies as well.
hope this helps.