For HDTraffic you need more than GPS: You also need a modem and a SIM card. Both have been offered by Tomtom in a cable which both charges the unit and has a modem/SIM built into the plug, but I am not sure if this service is still being offered by Tomtom now that they have LIVE services on the newer models.
Here is a link which is two years old:
If you can obtain this plug in your country AND if HDTraffic is being offered there, you might have success with it. Otherwise, stick with TMC as an alternative.