the suzuki swift has a great chassis on it, not sure if its in your budget, or if they do a small enough economical engine. my mother in law has a vw polo and she loves it, they did a 3 cyclinder diesel version, i did test drive one a while back when my wife had one as a test car. sounds odd but was quiet tight.
if you want really tiny, have a look at the proton savvy, my bodyshop has one as a loan car, it has a gutless engine and you really ahve to work it, but it costs £30 to fill up and takes for ever to drain the tank. and its built on a clio chassis.