U.K. pubs and restaurants opened Monday for indoor service for the first time since early January. Yet the prime minister sounded a cautious tone, warning about a more contagious COVID-19 variant that threatens reopening plans.Theatres, leisure venues and museums were also reopening as part of the latest step in easing nationwide restrictions, raising hopes that Britain’s economy may soon start to recover from the devastating effects of the pandemic.Andy Frantzeskos, a chef at Nopi, an upmarket Mediterranean restaurant in London’s Soho district, said he felt “a bit of anxiousness … but more excitement than anything.”“It’s been a long time coming since lockdown, so we’re all happy to be back and want to cook some good food,” he said.