I use the excelent software TomTom Navigator. I use it in conjunction with a Garmin GPS II+ GPS receiver and a Lowe magnetic antenna.
Here are some usefull addons for Navigator.
Speed Camera POI List
This is a Points Of Interest list of a large number of the UK speed cameras. The list is growing all the time.
This is an addon module for Navigator which monitors the POI lists and provides audio feedback on approaching points of interest.
audio files for CheckPOInt
A couple of audio files that I use with CheckPOInt.. One is a siren sound while the other is a voice saying 'speed camera 30 seconds'.
Do you have bluetooth?
Then this TomTom Bluetooth GPS receiver has got to be the easiest way. Just put it on the back parcel shelf of your car and that's it. You need to make sure you charge it up first though.
£256 from Expansys