I have an X1, which is great value considering its huge list of features, the only annoying feature is having to load the DVD map disc into the unit every time you want to go somewhere. A pain in the ass if your listening to a CD.
You can store an area of the map within the unit, say central birmingham, then you will not need to load the disc, if you and your destination are within this area.
dadwhitey will not have this problem when he adds sat nav to his 6600, as the dvd will be in a seperate unit. I also have a US model of the 6600, and its excellent, much nicer IMO than the x1, both asthetically and quality of picture.
If you can streach the funds, this may be an option, a pioneer avh6600, then add something like the avic-88dvd? i think.