Here in the U.S., the four varieties of peanuts grown commercially require a long growing season of at least 150 days of warm weather. They also require about twenty-two inches of water during the growing season (Source University of Georgia).
The site further states that during the 150 growing season, soil and air temperature cannot be less than 56 degrees F and that an average of 86 degrees F is optimal.
They require a light colored, sandy soilas well... Although I'm not entirely familiar with the U.K.'s growing season, I would imagine that's the major reason the venerable peanut cannot be grown there...