Have a look at:
www.pocketgpsworld.com Subscription is £19.99 for 12 months. You download the UK and Europe speed camera database onto a SD card put the card into the car and the data show as personal points of interest. Gives visible and audible alerts. Covers fixed and mobile sites. Weekly updates can be added to the SD card as forum members report new cameras.
Setting up is not as complex as the written instructions would suggest. If you go with them tweak the audio warnings to off or it will drive you mad additional with so many cameras set visibility to as approaching or your map will be filled with nothing but camera symbols.
Others may suggest using mobile phone apps but I have found this SD based system very reliable.