Just thought i would add my 2p for you Lucy
I have the Alpine CD-Rom based Nav system in my company car, with the fold out screen in the dash oh + TV and MP3 CD chager as well
. I have to say its a first class system and is faultles.
99.9% of all mapping is done by a company called Nav-Tec so all the maps will be the same, its how the company (equipment manifacturer) choses to put this infomation across to you the end user. I have used VDOs system and think its PAP in a word.
The Ipaq is a very good and cheap option as your looking at 1K minimum for a Screen and CDrom or DVD based unit.
The Nav-Man Jacket for the Ipaq is very good and the 3400 model offers voice as well, but you WILL have a problem with the front screen on the Clio yes. The Tom Toms version for the ipaq offers a remote external antenna that you can stick on the roof and just run the cable through the door its magnetic so you can take it on or off when ever you want + you get full use of the Ipaq as well like a nice MP3 juke box
Have a Look on ebay there are always loads of nav systems on there for sale !
Good Luck anyway
Cheers
matt