Weather - pure and simple and the cost to keep homes warm. The British Isles benefit from the Gulf Stream bringing warmer waters and thus generally warmer weather. While this is also somewhat true for the western coast of Norway, the benefit is just not as great.
Average temperatures in Oslo, Norway:
AVERAGE TEMPERATURE °C
January -7
February -7
March -2
April 3
May 9
June 14
July 15
August 14
September 9
October 5
November -1
December -5
Average Temperature for London, England,UK:
AVERAGE TEMPERATURE °C
January 4
February 4
March 6
April 8
May 12
June 15
July 17
August 17
September 14
October 11
November 7
December 5