I have seen something in one of those Sunday supplements (house of Bath catalogue I think) that looks a bit like a wooden clog.This goes into the shoe, and it has a screw at the end which you turn, and this opens up the wood which in turn stretches the shoe.
fill a leak proof bag with water, put it in the shoe, ensuring that it fits tightly and then freeze - the water expands stretching the shoe! Apparenly - not tried it yet but plan to!