I’ve also subscribed to the excellent Pocket GPS World site which is an fantastic source of information on all things GPS. For a small subscription the site offers speed camera locations as a point of interest download – much cheaper than TomTom’s own service.
Incidentally, my TomTom software was supposed to come with one month free access to their speed camera updates service. It’s never worked and TomTom’s email based support has been hopeless. A shame their support isn’t as good as their products.