Thanks for all your help.
I bought myself a Vista HCx in the end and used it in France. As a true baptism of fire, I never took any paper maps with me. (I could always go to a shop and buy one in France after all)
I found the unit easy to use. I did my usual, lets see what happens when I do this, and after about an hour, was pretty familiar to a very basic level of how to get it to do things.
I also bought the Mapsource mini SD card for Europe.
Wow! FF was right. Definitely worth having. Fantastic detail of roads and much better than I could have without carrying several panniers worth of local maps. That was definitely a big advantage. Very handy for finding my way through towns and finding minor roads alongside main roads for dodging traffic. With just a map, I tend to just bash down the main road, otherwise it's stop to get the map out every few miles. Nothing as far as geography goes, so no contours and nothing to show up all the bastard hills, but I never really bought a sat-nav for that, I just want it to keep me on track. I'd buy detailed maps if that was what I wanted.
A bigger screen would have been nice, I suppose. You don't get much area on the screen when you go for detailed mapping. I did zoom in and out a few times, but I found with it set with the scale at 1.2 miles, I could dodge around a small town via back lanes and that with 800ft, I could find a direct route through town along back street quite easily, with maybe a bit of zooming in when it got very fiddly. So yes, a bigger screen would be nice, but I wouldn't say essential, but I'm still very new to all this...
And yes, the base map in the sat-nav is pretty well rubbish, so an additional map is as good as essential. I can see how out of date even the latest mapping is, because living in Milton Keynes, things change very quickly. I tried looking for local restaurants and saw that it was already out of date, but these things change very rapidly. It sent me to an industrial estate in France when I was looking for food, but it soon came up with another.
I love the find facility on it! It meant that I could just keep riding and as soon as I was hungry or it was getting late, I could ask the sat-nav where the nearest supermarket, restaurant or hotel was and it would come up with several answers.
The goto thing was just crazy most of the time. Some of the things it came up with was just comical. It suggest I go home via Winchester from Guilford on my way home, so I tended to look for the way I liked and let the sat-nav keep throwing a tantrum and suggest different routes when I didn't follow it until it came up with something I liked. It was fantastic getting me through towns and cities.
I never had time to find out how to put a route into it from my computer.
It would have been handy to know beforehand that with a mini SD card, you can't put the mapping into your computer, but you can with the CD. But with the CD you can only put the mapping onto one GPS unit, whereas with the mini SD card, you can put the map into whichever unit you like. Although I suspect that there are ways around this, by hook or by crook.
Battery life was very good too. I bought my fast charger with me and 3 pairs of rechargeables from Maplins. I switched off the compass (The mapping told me which direction I was heading in anyway, so the compass seems redundant for using on road at least) and definitely got at least 20 hours from a set of batteries with the backlight on medium.
Plenty of other toys on the machine too. I've never bothered looking into altitude on rides before, but now I have an altimeter, I might look at it a bit and see how much climbing I can do instead of how many miles. I know they are a bit temperamental, but it's only for comparison and a bit of fun.
Plus all the other stuff on the cycle computer mode and altitude, with height gained per minute and so on. Yes all those bits of useless information that I like when there's not much else to think about and other numbers to chase after. All those little personal bests I can go for instead of just max speed, average and distance.
I amused myself on the ferry seeing how fast it was going and the altitude of the waves.
I expect that the way for me to put a route into the unit would be to plot the route on something like Bikey then transfer it into my GPS? I tried this with Google, but only managed to transfer waypoints, not a route to follow.
So, I still have a bit to learn, but overall, I'm dead chuffed with it.
Where does the panel think the best place is for storing a record of my tracks and planning routes to upload onto the unit for following?