Whatever you do, it's not good to use TomTom's Android apps. They are forcibly "retiring" the old separate apps for every country and are coming out with a new single app that lets you download free maps and traffic. After October 2015 the old apps will cease functioning. Why is this bad? Aside from the fact that they are ripping off customers of the old apps (giving an initial temporary discount but ultimately charging the full subscription), the new app charges a subscription for navigation!
Why are they doing this?
Because nobody is dumb enough to pay for subscriptions to map updates or traffic. Because no map is 100% accurate anyway, so people learn workarounds for those times when certain locations are missing and just keep the original map. Because traffic data isn't really all that useful because it's not up to the second, and traffic data that is even a few minutes old can often be completely useless by the time you get to the area supposedly affected. Commuters learn their own alternate routes anyway (or are just content to sit with everybody else), and travellers don't usually need it because they're not travelling those areas at those times.
So the only way for TomTom to get you to keep paying for something you've already bought is to change the business model so that the one reason navigation apps exist requires a subscription. Smart, but notveryuser friendly! Especially when they're yanking the rug out from under their own previous customers.
I've tried using the available channels to contact both Google Play and TomTom, and they are both staying ominously silent. No response at all, even to tell me I'm out of luck. So apparently Google is fully aware of the issue but has no intention of losing their chunk of TomTom's profits. But with any luck, users will make the right choice.