Try http://www.yachtingsoftware.com/
I recently bought an E95 and was told by two places locally that I'd need a new chart in MicroSD format because my ancient CF card couldn't be updated to MicroSD. Yaching Software sent me an 'update chart' for half the price of a new chart and it worked a treat. They seem to know their stuff.
No connection other than happy customer who's £100 better off because of a call to them.
I think the built-in chart is a basic Navionics Silver chart which can't be updated, as far as I know. The only update involves buying a Navionics Plus or Platinum chart for the area you'll be using it in and plugging it in. Give them a ring and see what they say.