I think the font was traditionally near one of the doors (west door?). The brasses are the flat plates, set into the floor with a life-size low relief figure of the memorialised person - a knight or noble most often. The screen, called a rood screen, separated the sacred area around the altar from the congregation - those I've seen were wooden with gilding, solid up to about waist height, then open with tracery or lattice work up to well above head height, ending in a heavy beam that supported a cross in the centre and possibly other decorative elements (heraldic crests os sponsoring families or guilds say); there was an open arch that spanned the ailse.