It was a power cut, and was off for just over an hour.

And after spending more time trawling the internet, I have fixed it.

Although I had to set the date and time back up after the power cut, it was set 3 minutes different to the time that was showing on my phone, so I set the TV to get the time from the network and it fixed it there and then. So all caused by the time being 3 minutes out. I'm not sure why Netflix carried on working whereas all other apps said there was no internet connection, but now it's fixed I won't worry about it.