I got my tom tom one for £159.99 in the sale in Halfords too, seems to be good, although I've not really had the need to use it properly yet. It's easy to use though, can just go straight into any car, no need to fit any of the extra bits, which is what I wanted, and works with the uv windscreen.
I thought the screen mount was ace !! Can hardly get the bugger off !!
Dont think they are meant to be wet. Attach it dry.
Heres a link though for additional mounts. http://www.brodit.com/