I agree with Kremmen re-investigate the TomTom.
I have an old style TomTom One (not the new slimline version) which I bought a few years ago for around £120, its one of the best devices I have ever bought.
The traffic update and the speed camera locations can be downloaded via their website through a program called TomTom Home, once on your PC it automatically downloads all updates for the location of speed camera's and any program software updates.
The TomTom Home software is free however the traffic and speed cameras have a yearly subscription of around £40 if bought at the same time.
The traffic information is as Kremmen says works via your bluetooth enabled phone, you can indeed set the update times from anything from 5mins to I think 1Hour, the cost of the update check is minimum and depending on your phone tariff may be included in your monthly charge (luckily mine is!).
All the program software, maps, traffic updates and speed camera locations are all built in to one unit, the only thing you may need as an extra is a larger SD memory card to fit any extra maps you may need, these cost around £50 each but are well worth it. Depending on which TomTom you go for however you may get all the european maps included in the price.
The only cable that is required is a charging wire which I have running down the lefthand side of the radio(not really a problem!).
If mounting the unit on the windscreen is a problem for you, I'm pretty sure that a Brodik clip(Think thats what its called!
) can be used to mount the TomTom to an air vent!
TomTom is for me the way to go and would recommend it to anybody (no I'm not on commission
After using Tom Tom I couldn't warrant spending over a £1000 on an inbuilt sat nav device when I can spend a couple of hundered on a Tom Tom that is not only upgradable but can be used in the wifes car as well.
The only thing I wouldn't use on the TomTom is the handsfree option you can get on some of the more expensive versions, don't pay extra for this it's rubbish!
Hope this sheds a little light on TomTom for you.