it tends to be when the majority of the population feels that times are really hard, that the message of extremists gets listened to. the classic example of this was in Germany in the 1920s - once the german economy began to recover from the crisis that followed WW1, support for the nazis all but evaporated, sinking to less than 3% in 1928. (the wall street crash changed all that).
Britain's economy is still definitely not the best, but we're in a better place than we were in 2010, and unemployment has fallen by 3% since 2012. the extremist view, whether left or right, is currently irrelevant.