Just in case others with Samsung TVs are having problems!
Since 24/2/15 there have been problems for some models (D & E) of Samsung's Smart TV connecting to the internet.
The problem looks like a DNS type of thing that the customer might be able to fix.
I've wasted a lot of time troubleshooting this before (thanks to Twitter) finding out it's a world-wide issue!
This site has a good summary: