If you just look at the headlines of the British and French elections you would never know just how important the political left factored into these elections.
In Britain, the Labour Party had an overwhelming victory over the Tory Party. However, it wasn't so much a victory for Labour as it was a defeat for the Tories.

and the analogies with Sanders and the US only go so far.

Politics in the US, Britain, and Europe in general are being upended, I'd caution against pigeon holing things into the old left/right, Dem/Repub, Tory/Labor, scenario.