I just spoke to Expansys who said that the cable would work and the to the makers - Proporta (UK). They said that the website information was incorrect. The cable is a sync only cable and will not charge the UX50.
Sorry to be the bearer of bad news.
BTW anyone know a UK source for a car charger for the UX-50 Iam having no look whatsoever in the usual places.
You cannot charge without either the cradle or 1 of the Exim style leather cases with a usb charger inside... If you have 1 of these cases then you can use that cable as a charger... and Mark, if you get 1 of these cases they also sell cigarette lighter adaptors for usb cables, I have 1 and it works quite well as does the ac adaptor. Now if I go on a trip I can just take the usb cable with the car and ac adaptor and charge almost anywhere...
The leather case if the best alternative. I can hotsync and charge my UX50 with the same USB/Sync cable. I've even charged my UX50 from my laptop battery.
Check out the leather case from the following link: