Completely agree with easyflyer83...
Think Aer lingus - think Ireland
Think Norwegian - think Scandinavia
It will take some HEAVY marketing to get the UK general public to think Norwegian = Arrecife or Pula once or twice a week.
Gatwick is saturated with a lot of the routes chosen. Just look at Barcelona for instance.
I still think Stansted or even Luton would have been a better option, but even still some major marketing and brand awareness in these areas would be needed.