Had to fish around to find this but looks like there's 4 available.
Use the attached voucher to get to this price. Quidco available @ 3%.
Latest maps of UK and Ireland
Large 4.3" touchscreen with 3D graphics
Unique new TomTom Map Share technology
Speech recognition for address input
Transmits sound to your car stereo
QuickGPSfix software for fast startup
Record you own voice directions
Enhanced hands-free calling
Pre-installed saftey camera database
Play your own MP3's from an SD Card on the 520's FM transmitter