What I did was create a raster surface of net commuting (by district) for the whole UK in 2001 (the latest data). Then I created a flow map vector layer for the UK at district level. Then I chopped out Greater London, displayed only those flows of more than 1,500 commuters, and put this together with the raster layer. The final image communicates a lot of information quite simply.
In the image below (click on it to view full size), the red peaks are areas of high in-commuting and the blue troughs are areas of out-commuting. The flow lines illustrate the spatial patterns of movement. Note the area of high in-commuting to the west of London - the Heathrow effect.
