It has been said many times before that GEs are lost rather than won, and the elections in France and the UK support that view.
The people did not like the way their countries were run by the incumbent governments so wanted change. Neither election, imo, prefaces a sea change in the stance of the electorate towards any ideology but just a temporary change of balance based on current dissatisfaction.
In France there was the option of moving their votes to parties to the left or the right of a centrist government so both sides benefited (and suffered) as a result. It was great to see a large vote for the left but that was probably as a last minute reaction to the real fear of getting a far right victory. In this country there was little or nothing tangible to offer from the Labour Party on the centre-left, other than not being the Tories, so people went with the xenophobic, populist promises of Reform, even though they were just the Tories on steroids, and to some extent to the LDs and Greens. Who knows what would have happened had a more left wing party been set up to fight Labour and add more choice to the vote.