OK. If anyone is interested, I should have took more pictures as this was easy. On the Binatone F430 and I would presume others will be similar. Take out the stylus. Use a hard thin piece of plastic like a credit card and from the open corner where the stylus sat prise open the back cover along the top. (comes away easier than the side) Once you have went round the sat nav the back cover will fall off in your hand and you have this
Sorry, poor quality
^^ In the red circles is the six small Phillips screws you need to undo. Once undone very carefully prise the front screen off. Now be warned. It looks like a bezel round the screen (its not) Once apart the screen is attached to the board just like a laptop keyboard/mouse and some screens.
Below is the back of the screen showing the ribbon cable.
The ribbon cable is connected into this part of the board
You have a black part of this connection. You gently prise that up and slide the ribbon out. To put one in just slide in place (straight) and snap down the black bar.
Also in that picture you should see the battery number if any of you need to google for a new one. Hope this makes sense.