LONDON—U.K. Prime Minister Theresa May’s Conservative Party avoided widespread losses in local elections across England but ceded some key seats, presenting a mixed picture for the British leader in her first electoral test since losing her party’s parliamentary majority last year.
With most of the results in Friday, the main opposition Labour Party came away without decisive gains, suggesting it failed to fully capitalize while the Conservative government faces battles on several fronts. Voting took place in 150 local councils...