British Airways used to fly to both Bergen and Stavanger - now they don't
SAS fly London-Stavanger but not London-Bergen
That left Norwegian with a very dominant position on these 2 routes. I don't think flying via Amsterdam, Copenhagen or Oslo will be considered an effective substitute or (in the case of Amsterdam as strong competition
There may well be room for a Wizz on London-Bergen (in particular) and, maybe to a lesser degree, also on London-Stavanger. I would be interested to know if Wizz can pick up any oil/gas traffic to Stavanger though